Is my build-vs-buy call actually right, or just clear?
You made the call. The columns add up, the timeline looks sound, and you feel settled. That feeling is not proof. It only means you stopped looking. Most build-vs-buy mistakes are not math errors. They are blind spots — the maintenance burden nobody priced, the vendor lock-in nobody tested, the team capacity you assumed instead of checked. The damage shows up months later, when it is expensive to undo. You cannot think your way out of a blind spot, by definition. You can only hunt for it. This page will not hand you a better formula. It will make you name what you have not checked, before reality checks it for you.
Clear is not correct. Your spreadsheet can be tidy and still be wrong, because it only counts what you remembered to count. The fix is not more analysis. List every assumption you have not tested. Price what it costs to reverse this choice later. That is the real work.
What changes unlock by starting
- A written list of assumptions you can test, instead of a feeling you trust.
- A real number for what reversing this decision would cost.
- Honesty about the one risk you have been avoiding.
- A decision you can explain to someone who was not in the room — and defend.