Without benchmarking LLMs, you're likely overpaying 5-10x

(karllorey.com)

71 points | by lorey 7 hours ago ago

51 comments

  • hamiltont 5 hours ago ago

    Anecdotal tip on LLM-as-judge scoring - Skip the 1-10 scale, use boolean criteria instead, then weight manually e.g.

    - Did it cite the 30-day return policy? Y/N - Tone professional and empathetic? Y/N - Offered clear next steps? Y/N

    Then: 0.5 * accuracy + 0.3 * tone + 0.2 * next_steps

    Why: Reduces volatility of responses while still maintaining creativeness (temperature) needed for good intuition

    • pocketarc 5 hours ago ago

      I use this approach for a ticket based customer support agent. There are a bunch of boolean checks that the LLM must pass before its response is allowed through. Some are hard fails, others, like you brought up, are just a weighted ding to the response's final score.

      Failures are fed back to the LLM so it can regenerate taking that feedback into account. People are much happier with it than I could have imagined, though it's definitely not cheap (but the cost difference is very OK for the tradeoff).

    • Imustaskforhelp 5 hours ago ago

      This actually seems really good advice. I am interested how you might tweak this to things like programming languages benchmarks?

      By having independent tests and then seeing if it passes them (yes or no) and then evaluating and having some (more complicated tasks) be valued more than not or how exactly.

      • hamiltont 4 hours ago ago

        Not sure I'm fully following your question, but maybe this helps:

        IME deep thinking hgas moved from upfront architecture to post-prototype analysis.

        Pre-LLM: Think hard → design carefully → write deterministic code → minor debugging

        With LLMs: Prototype fast → evaluate failures → think hard about prompts/task decomposition → iterate

        When your system logic is probabilistic, you can't fully architect in advance—you need empirical feedback. So I spend most time analyzing failure cases: "this prompt generated X which failed because Y, how do I clarify requirements?" Often I use an LLM to help debug the LLM.

        The shift: from "design away problems" to "evaluate into solutions."

    • piskov 3 hours ago ago

      How come accuracy has only 50% weight?

      “You’re absolutely right! Nice catch how I absolutely fooled you”

    • lorey 5 hours ago ago

      Yes, absolutely. This aligns with what we found. It seems to be necessary to be very clear on scoring (at least for Opus 4.5).

    • 46493168 4 hours ago ago

      Isn’t this just rubrics?

      • 8note 3 hours ago ago

        its a weighted decision matrix.

  • andy99 5 hours ago ago

    Depends on what you’re doing. Using the smaller / cheaper LLMs will generally make it way more fragile. The article appears to focus on creating a benchmark dataset with real examples. For lots of applications, especially if you’re worried about people messing with it, about weird behavior on edge cases, about stability, you’d have to do a bunch of robustness testing as well, and bigger models will be better.

    Another big problem is it’s hard to set objectives is many cases, and for example maybe your customer service chat still passes but comes across worse for a smaller model.

    Id be careful is all.

    • candiddevmike 5 hours ago ago

      One point in favor of smaller/self-hosted LLMs: more consistent performance, and you control your upgrade cadence, not the model providers.

      I'd push everyone to self-host models (even if it's on a shared compute arrangement), as no enterprise I've worked with is prepared for the churn of keeping up with the hosted model release/deprecation cadence.

      • andy99 5 hours ago ago

        How much you value control is one part of the optimization problem. Obviously self hosting gives you more but it costs more, and re evals, I trust GPT, Gemini, and Claude a lot more than some smaller thing I self host, and would end up wanting to do way more evals if I self hosted a smaller model.

        (Potentially interesting aside: I’d say I trust new GLM models similarly to the big 3, but they’re too big for most people to self host)

    • jmathai 5 hours ago ago

      You may also be getting a worse result for higher cost.

      For a medical use case, we tested multiple Anthropic and OpenAI models as well as MedGemma. Pleasantly surprised when the LLM as Judge scored gpt5-mini as the clear winner. I don't think I would have considered using it for the specific use cases - assuming higher reasoning was necessary.

      Still waiting on human evaluation to confirm the LLM Judge was correct.

      • andy99 4 hours ago ago

        You obviously know what you’re looking for better than me, but personally I’d want to see a narrative that made sense before accepting that a smaller model somehow just performs better, even if the benchmarks say so. There may be such an explanation, it feels very dicey without one.

      • lorey 4 hours ago ago

        That's interesting. Similarly, we found out that for very simple tasks the older Haiku models are interesting as they're cheaper than the latest Haiku models and often perform equally well.

    • lorey 5 hours ago ago

      You're right. We did a few use cases and I have to admit that while customer service is easiest to explain, its where I'd also not choose the cheapest model for said reasons.

  • epolanski 5 hours ago ago

    The author of this post should benchmark his own blog for accessibility metrics, text contrast is dreadful..

    On the other hand, this would be interesting for measuring agents in coding tasks, but there's quite a lot of context to provide here, both input and output would be massive.

    • lorey 4 hours ago ago

      Pushed a fix. Could you check, please?

      Any resources you can recommend to properly tackle this going forward?

    • lorey 4 hours ago ago

      Appreciate the feedback, will work on that.

      • epolanski 3 hours ago ago

        Do you have any insights on the platform evaluation for coding tasks?

      • faeyanpiraat 4 hours ago ago

        One more vote on fixing contrast from me.

        • lorey 4 hours ago ago

          Will fix, thanks :)

          • faeyanpiraat 4 hours ago ago

            Tried Evalry, its a really nice concept, thanks for sharing it!

  • verdverm 5 hours ago ago

    I'd second this wholeheartedly

    Since building a custom agent setup to replace copilot, adopting/adjusting Claude Code prompts, and giving it basic tools, gemini-3-flash is my go-to model unless I know it's a big and involved task. The model is really good at 1/10 the cost of pro, super fast by comparison, and some basic a/b testing shows little to no difference in output on the majority of tasks I used

    Cut all my subs, spend less money, don't get rate limited

    • dpoloncsak 5 hours ago ago

      Yeah, one of my first projects one of my buddies asked "Why aren't you using [ChatGPT 4.0] nano? It's 99% the effectiveness with 10% the price."

      I've been using the smaller models ever since. Nano/mini, flash, etc.

      • sixtyj 5 hours ago ago

        Yup.

        I have found out recently that Grok-4.1-fast has similar pricing (in cents) but 10x larger context window (2M tokens instead of ~128-200k of gpt-4-1-nano). And ~4% hallucination, lowest in blind tests in LLM arena.

        • verdverm 4 hours ago ago

          [flagged]

          • rudhdb773b 4 hours ago ago

            Grok is the best general purpose LLM in my experience. Only Gemini is comparable. It would be silly to ignore it, and xAI is less evil than Google these days.

      • phainopepla2 5 hours ago ago

        I have been benchmarking many of my use cases, and the GPT Nano models have fallen completely flat one every single except for very short summaries. I would call them 25% effectiveness at best.

        • verdverm 4 hours ago ago

          Flash is not a small model, it's still over 1T parameters. It's a hyper MoE aiui

          I have yet to go back to small models, waiting for the upstream feature / GPU provider has been seeing capacity issues, so I am sticking with the gemini family for now

      • walthamstow 5 hours ago ago

        Flash Lite 2.5 is an unbelievably good model for the price

    • r_lee 5 hours ago ago

      Plus I've found that overall with "thinking" models, it's more like for memory, not even actual perf boost, it might even be worse because if it goes even slightly wrong on the "thinking" part, it'll then commit to that for the actual response

      • verdverm 4 hours ago ago

        for sure, the difference in the most recent model generations makes them far more useful for many daily tasks. This is the first gen with thinking as a significant mid-training focus and it shows

        gemini-3-flash stands well above gemini-2.5-pro

    • dingnuts 5 hours ago ago

      [dead]

  • gridspy 5 hours ago ago

    Wow, this was some slick long form sales work. I hope your SaaS goes well. Nice one!

  • empiko 3 hours ago ago

    I do not disagree with the post, but I am surprised that a post that is basically explaining very basic dataset construction is so high up here. But I guess most people just read the headline?

  • deepsquirrelnet 5 hours ago ago

    This is just evaluation, not “benchmarking”. If you haven’t setup evaluation on something you’re putting into production then what are you even doing.

    Stop prompt engineering, put down the crayons. Statistical model outputs need to be evaluated.

    • andy99 5 hours ago ago

      What does that look like in your opinion, what do you use?

    • lorey 4 hours ago ago

      This went straight to prod, even earlier than I'd opted for. What do you mean?

      • deepsquirrelnet 3 hours ago ago

        I’m totally in alignment with your blog post (other than terminology). I meant it more as a plea to all these projects that are trying to go into production without any measures of performance behind them.

        It’s shocking to me how often it happens. Aside from just the necessity to be able to prove something works, there are so many other benefits.

        Cost and model commoditization are part of it like you point out. There’s also the potential for degraded performance because of the shelf benchmarks aren’t generalizing how you expect. Add to that an inability to migrate to newer models as they come out, potentially leaving performance on the table. There’s like 95 serverless models in bedrock now, and as soon as you can evaluate them on your task they immediately become a commodity.

        But fundamentally you can’t even justify any time spent on prompt engineering if you don’t have a framework to evaluate changes.

        Evaluation has been a critical practice in machine learning for years. IMO is no less imperative when building with llms.

  • OutOfHere 4 hours ago ago

    You don't need a fancy UI to try the mini model first.

  • petcat 5 hours ago ago

    > He's a non-technical founder building an AI-powered business.

    It sounds like he's building some kind of ai support chat bot.

    I despise these things.

    • montroser 5 hours ago ago

      The whole post is just an advert for this person's startup. Their "friend" doesn't exist...

    • lorey 4 hours ago ago

      Totally agree with your point. While I can't say specifically, it's a traditional (German) business he's doing vertically integrated with AI. Customer support is really bad in this traditional niche and by leveraging AI on top of doing the support himself 24/7, he was able to make it his competitive edge.

    • r_lee 5 hours ago ago

      And the whole article is about promoting his benchmarking service, of course.

    • njhnjh 5 hours ago ago

      [flagged]

      • sullivanmatt 5 hours ago ago

        It's perfectly possible it's someone with deep domain experience, or someone who has product design or management skills. Regardless, dismissing these people out of pocket is not likely the best choice.

        • 5 hours ago ago
          [deleted]
  • 5 hours ago ago
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  • nickphx 5 hours ago ago

    ah yes... nothing like using another nondeterministic black box of nonsense to judge / rate the output of another.. then charge others for it.. lol

    • coredog64 4 hours ago ago

      Amazon Bedrock Guardrails uses a purpose-built model to look for safety issues in the model inputs/outputs. While you won't get any specific guarantees from AWS, they will point you at datasets that you can use to evaluate the product and then determine if it's fit for purpose according to your risk tolerance.