Build vs Buy: Making Smart Decisions About Custom LLM Models
What you'll learn
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Building your own model means fine-tuning a foundation or frontier model (often an open-source one) on your organisation's historical knowledge. It makes most sense when the task is highly domain-specific and involves confidential or proprietary information the off-the-shelf models simply don't know about.
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The build side carries three real costs: assembling and validating a large training dataset, paying for the compute to train on it (the same GPU spend that has OpenAI and Anthropic burning billions), and keeping pace as the underlying open-source models improve, so you don't trap yourself frozen on one model version forever.
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For work that isn't hyper-specific, collating, comparing or applying common-sense understanding to incoming data, you're usually better off using what comes off the shelf and picking the right model for the job.
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Match the model to the task on accuracy versus cost and performance. Tom notes that for a job like Tableau-related accuracy he'll reach for Opus, but running Opus across bulk data manipulation or validation would be slow, expensive and overkill; a cheaper Sonnet or Haiku-class model often works more efficiently.
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If you have Bedrock or a similar platform with an array of models from different providers, spend real time testing and validating your workload across them. Don't 'go big or go home', find the model in the middle that does what you need.
By the end of this episode you should be able to decide when a custom domain-specific LLM is worth its training and maintenance costs, and when to instead test off-the-shelf models to find the best accuracy-cost-performance trade-off for your workload.
In this episode
- Build versus buy: the two schools of thought
- When building a domain-specific model makes sense
- The three hidden costs of building your own model
- Lessons from the AWS Expo: AIDoc's domain model
- Buying off the shelf: matching the model to the task
- Accuracy versus cost and performance trade-offs
Tom explores the critical decision between building custom LLM models versus using off-the-shelf solutions. Drawing from insights at the AWS Expo, he breaks down the real costs, challenges, and strategic considerations for organizations evaluating domain-specific AI implementations.
Build vs Buy: Making Smart Decisions About Custom LLM Models
Key Topics Covered
When to Build Custom LLM Models
Domain-specific applications requiring specialized knowledge
Handling proprietary or confidential information
Real-world example: AIDoc's experience at AWS Expo
Understanding your organization's unique requirements
True Costs of Building
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Data Preparation
Gathering organizational historical knowledge
Creating validation and training datasets
Organizing proprietary information
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Training Expenses
GPU infrastructure costs (billions spent by OpenAI, Anthropic monthly)
Ongoing computational requirements
Budget considerations for organizations
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Maintenance & Updates
Keeping pace with base model improvements
Avoiding being locked into outdated versions
Continuous investment requirements
When to Buy Off-the-Shelf
Non-hyper-specific use cases
Data collation and comparison tasks
General analysis and processing needs
Cost-effective solutions for standard workflows
Optimizing Model Selection
Using platforms like AWS Bedrock for model diversity
Balancing accuracy vs. cost vs. performance
Example: Claude Opus vs. Sonnet vs. Haiku trade-offs
Avoiding "overkill" with expensive models
Testing and validation strategies
Key Takeaways
Don't default to the most expensive model
Test multiple options before committing
Understand total cost of ownership for custom builds
Match model capabilities to actual requirements
Consider the rapid pace of AI ecosystem changes
Mentioned Companies/Platforms
AWS (Amazon Web Services)
AWS Bedrock
AIDoc
OpenAI
Anthropic (Claude models: Opus, Sonnet, Haiku)
Resources
AWS Expo insights and presentations
Open source foundation models for custom building
Chapters
0:02 - Introduction: The Build vs Buy Debate
0:25 - When Building Custom Models Makes Sense
2:02 - The Real Costs of Building Your Own Model
3:35 - Real-World Example: AIDoc at AWS Expo
4:09 - The Case for Off-the-Shelf Solutions
5:44 - Optimizing Model Selection and Cost
6:46 - Final Recommendations and Wrap-Up
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Explore AI ServicesTranscript
So today I wanted to have a quick discussion about sort of build versus buy when it comes to, um, different LLM models. So the reason I bring this up is because it comes up in, in discussion like reasonably frequently. And, you know, there's two, two thoughts, there's two schools to this argument. So if you're trying to do something that is particularly specific to a certain domain that you operate in, then taking a foundational model, uh, frontier model, and then building on top of it, one of the open source ones, of course, building on top of it to be able to add more domain specific information can be a very effective way of building an LLM supercomputer, so to speak, um, that allows your model to do something that's very domain specific. Now, of course, in doing that, it's going to cost both time and money in a number of different ways.
And so I just want to sort of touch upon what some of these different, you know, issues might be, especially as you look forward at the rate of knots that stuff changes inside of this, uh, ecosphere at the moment. So if you were to build your own model, first of all, of course, what you need to be able to do is get a lot of validation training data put together and come up with a plan to allow you to be able to actually build that stuff out. So, you know, you need to be able to get your entire organization's worth of historical knowledge, stick that together and, you know, start training your model on, you know, what some of the, uh, issues are, some of the things that you want to be able to like raise with the, the, uh, platform that you're doing. Then on top of that, you also need to start thinking about the cost of actually training it because of course training an LLM is not cheap as we know, because, you know, open AI, Anthropic and what have you are spending billions of dollars, you know, on a monthly basis to pay for all the GPUs that they need to be able to train the models. So like, you know, when it comes to actually expanding that model further, you're going to have to spend a lot of cash training your, training your model.
And of course that might be worthwhile, but this is the type of stuff that you need to be able to, to ascertain. Is it, is it, is it worth the payoff when it comes to, uh, building a dedication model? And the third thing of course is that these models, the underlying models, the open source models that you're going to build on improve over time. And so as those models continue to improve, assuming that you want to be able to keep up and leverage some functionality that's in the underlying model that would improve the performance of your new model, you have to be able to of course account for that as well. You don't want to like, probably don't want to train a model and then be stuck on that model version forever.
And so, you know, when it comes to build versus buy, the build side of it can be quite a costly experience. Um, but I was down at the AWS expo last week and, um, watched a talk by, uh, AI doc and the experience they had in terms of building a domain specific model out for the stuff that they were doing. And it made a lot of sense. You know, if you're looking to do something that is super specific and it also involves probably a lot of confidential or proprietary information that the open source models may not know about, then, you know, building your own model makes a lot of sense. Now the flip side of that of course is if you're trying to do something that is not hyper specific, but requires some degree of, um, you know, thought and common sense being applied to data that's coming into your system, then there's also an element of, well, just use what comes off the shelf.
So if you weren't doing something that's particularly domain specific and instead was doing something that was the collation of data or comparing of data or understanding something that's going on in your dataset, well then conversely what you can do is figure out which model works best for what you're trying to do. Because for example, give you another one. If I'm using Claude code, I'm probably using Opus because I don't need the stuff that's in Fable and the other, you know, Sonnet and Haiku models are not going to be accurate enough for what I want to be able to do. So I'm probably going to use Opus and I'm probably not going to fiddle around too much. But if I was building out a LLM process to do something like data manipulation or data comparison or whatever, Opus would A, be pretty slow.
B, it would cost quite a lot of money. And C, I'm suspecting would be overkill for most things that I would like need to do. And so if you've got access to Bedrock or, um, you know, another similar platform where you've got an array of different models from different providers to do different things, ensure that you spend some time figuring out, you know, the accuracy versus cost and performance trade-offs because they're definitely there. And so if you're spinning up a process that requires some element of, you know, I don't know, data validation or whatever, and you want to use an LLM to do it, that's cool. But you don't necessarily have to pay for the most expensive model every time.
You might just get away with paying for, you know, the more affordable ones, ones that are going to work more effectively, more efficiently for what you need them to do. Don't just like, don't just go big or go home. Try and find something in the middle. That's just my thoughts on it. So like, if you want to be able to, or if you want to be, build your own model, just make sure that you understand the, uh, what's involved before you start doing that because you might end up trapping yourself in a scenario you don't want to be in.
And then if you want to be able to build stuff or buy stuff off the shelf, sorry, ensure that you test and validate whatever you want to be able to do with the different models, but to find the model that works best for what you want to do. That's it. That's my thoughts for the day. Happy Monday. Um, my name is Tom.
I will be back for another AI briefing soon enough. Um, bye for now. Why hire when you can partner? Concept Cloud's leading engineers build your startup's prototype without the overhead. Launch faster.
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Further reading
Build vs Buy Sanctions Screening
The same build-versus-buy calculus worked through on a concrete, high-stakes domain problem.
Not all AI is created equal
The written thesis behind the episode's core point: pick the model for the task rather than defaulting to the biggest one.
AI Data Preparation & Agentic Workflows
Building a domain model starts with assembling and validating the training data, which is exactly this work.
AI Readiness Audit
How to ascertain whether building a dedicated model is worth the payoff before you commit the time and compute.
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