In my eyes, you neglect the opportunity cost of "using one tool for everything": You end up with a solution that is much harder to mantain, since the wheel will

In my eyes, you neglect the opportunity cost of "using one tool for everything": You end up with a solution that is much harder to mantain, since the wheel will have been re-inventend many times over and sprinkled with bugs along the way. Given a problem of fixed complexity, at some point costs will rise when fewer tools are used. In summary: There is a "too much" and a "too few" when it comes to the number of tools used in a project. Where in that spectrum the OP is falling, we can't possibly know without knowing more details. Maybe the cost could have been smaller, maybe they hit an optimum and costs couldn't have been reduced by fewer tools (or more tools).