When every workflow has both a build path (custom AI tooling) and a buy path (vendor product), the decision framework matters more than the technology. This is the decision tree we use with B2B clients to choose between building, buying, or a hybrid approach.
If your competitive advantage depends on a specific AI capability — pricing optimization unique to your data, a recommendation engine on proprietary signals — build it. Vendors will commoditize anything generic, but they cannot replicate your data.
Some workflows touch so many systems (CRM + ERP + data warehouse + custom app) that no vendor can integrate deeply enough without custom work. In those cases, build the integration layer yourself even if you use vendor AI underneath.
At very high volume, per-token vendor pricing can exceed the cost of running your own deployment of an open-weight model. Most $5M-$50M companies are nowhere near this threshold; if you are, you know.
Meeting transcription, calendar scheduling, email triage, contract review — these are horizontal capabilities that thousands of companies need. Vendors will be better at them than you can be. Buy.
If you need it working in 30 days, you cannot build it. Vendor products ship in days. Building takes months. For most operational improvements, that gap is decisive.
If the underlying model improvements would force you to rebuild every 6 months, let the vendor absorb that work.
For mid-market B2B, the most common pattern is hybrid: buy the AI infrastructure, build the thin layer on top that captures your unique workflow.
Concrete example: buy Claude Team or Enterprise (do not build your own LLM). Build a Project loaded with your specific knowledge, your specific system prompt, your specific workflow. The total build cost is small (days, not months) and the differentiation comes from your data, your prompts, and your workflow design — not from the model.
Almost every successful AI deployment in the $5M-$50M segment we have seen is hybrid. "Build" and "buy" as polar opposites is a 2015 framing. The 2026 framing is "which layers do you buy, which do you customize."
| Option | Year 1 cost | Year 2-3 ongoing | When it fits |
|---|---|---|---|
| Buy (vendor SaaS) | \$20K-\$80K typical | Renewals + expansion | Horizontal workflow, urgency, no engineering capacity |
| Hybrid (LLM platform + your config) | \$10K-\$50K (platform + Treetop-style implementation) | Platform fees + occasional refresh | Most B2B workflows |
| Build (custom on top of API or open weights) | \$150K-\$600K + engineering FTE | Sustained engineering | Truly core capability, sufficient scale, engineering team |