Decide Whether to Do It In-House or Buy It In

    You are helping me make a make-versus-buy decision properly.

What I need: {{capability_or_function}}
Current situation: {{doing_it_now_or_starting_fresh}}
Vendor option: {{vendor_and_price}}
In-house option: {{who_would_do_it_and_what_it_takes}}
How core is this to what we sell: {{core_or_supporting}}
Timeline pressure: {{when_needed}}

Part 1 — Total cost, both sides, over three years.

Buy: subscription or fees, implementation, data migration, integration, training, admin time, the price rise at renewal, and the cost of exit if you leave. Include the seat count you will actually be on in year three, not year one.

In-house: fully loaded people cost including on-costs, not salary. Tooling and infrastructure. The opportunity cost of what those people are not doing instead. Maintenance forever, which is where in-house estimates always break — the build is the cheap part. Key-person risk: what happens when the person who built it leaves.

Show both as a three-year total and as a per-period run rate, and say which assumptions the comparison is most sensitive to.

Part 2 — The parts cost does not answer.
- Is this core? Building your differentiator is usually right even when buying is cheaper. Building your payroll system almost never is.
- Speed: what is the delay worth? A vendor live in three weeks against a build live in nine months is not the same product.
- Control: can you live with the vendor's roadmap, limits, and outages?
- Data: whose is it, can you get it out, and in what format?
- Lock-in: how hard is it to leave in year three, and does that change the renewal negotiation?
- Compliance: which option puts obligations on you that you cannot meet?

Part 3 — Consider the middle options explicitly, because they are usually best and rarely on the table: buy the commodity part and build the thin differentiating layer on top; outsource temporarily while you decide; a contractor build with an in-house handover; do it manually a while longer and let volume tell you.

Finish with a recommendation, the strongest argument against it, and the one fact that would flip the decision.