Preproduction code was always cheap or even free. Sales people have been selling software that didn't do what was on the tin since the dawn of time. Those features cost 0 dollars to write!

Production code. Especially production code with bugs is expensive. It can cost you customers, you can even get negative money for it in the form of law suits.

Coding agents are great for preproduction and one offs. For production I really wouldn't chance it at any scale above normal human output.