An AI feature that nobody uses is not free. It has three separate cost lines, only one of which stops when usage does, and the largest of the three is usually the one that is never written down. Here is how to total them with your own numbers, and what could have been known before the build started. Three cost lines, not one The usual accounting for an unadopted feature is engineering time, treated as sunk and therefore ignored. That undercounts badly, because two of the three li...