Should You Build Your AI Feature or Buy It?
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The economics changed
Building AI capability used to mean training models, which meant a data science team. Now it usually means calling an API with good prompts, retrieval and evaluation — which a competent development team can do.
That has shifted the build-or-buy line considerably towards building, particularly where the AI is one step inside a larger workflow.
Buy when
- The problem is standard: transcription, translation, general document extraction, meeting notes
- A mature product exists with a real customer base in your sector
- You need it working in weeks rather than months
- The volume is modest enough that per-unit pricing is comfortable
- Nobody internally will own a bespoke system
Build when
- The AI step sits inside a workflow specific to your business
- Data residency or confidentiality requirements rule out the available products
- Product pricing becomes uneconomic at your volume
- You need it embedded in your own interface rather than in someone else's
- The output must feed systems no product integrates with
The most common trigger we see is the fifth one. The AI part works fine in the product; getting the result into the operational system is the problem, and that is a build.
The hybrid nearly everyone ends up with
Buy the model capability from a provider, build the workflow, evaluation and interface around it. That is what most custom AI projects actually are — not model training, but careful assembly.
It gives you control of the parts specific to your business and someone else's investment in the parts that are not.
Cost comparison, honestly
| Buy | Build | |
|---|---|---|
| Time to working | Weeks | 2–4 months |
| Upfront cost | Low | £15,000–£40,000 typical |
| Running cost | Per seat or per unit | Model API usage, usually lower |
| Control of quality | Limited | Complete |
| Integration depth | What they offer | Whatever you need |
| If you leave | Data export, if provided | It remains yours |
A sensible sequence
Buy something to establish whether the capability helps at all. If it does and the limits bite — pricing, integration, quality on your data — build the version that fits.
That sequence costs a few months of subscription and removes most of the risk from the build decision.
Frequently asked questions
Do we need our own model?
What if we build and models improve?
Is building risky without in-house AI skills?
How long does a custom AI feature take?
Product almost fits but not quite?
That is the usual position. Tell us where it falls short and we will say whether building the gap or the whole thing makes more sense.