Most teams start AI cost control with a spreadsheet: model A costs this much, model B costs that much, so use the cheaper one.
That helps for a week. Then production traffic arrives.
The real cost problem is not the model price. It is losing the path between a user request and the billable provider call.
Once a product has multiple features, API keys, environments, retries, and fallback routes, the invoice stops answering the question founders actually care about:
Which product path created this spend, and could we have routed it better?
