I am a developer who also has some experience paying other developers for a project.
I do not agree with some of the criticism you are getting. If you say up front you won't pay for bugs then the developer should not accept the work if they don't want to work under those conditions.
It is easy to say "all code has bugs" but it is also true that cleaner and well thought out code will have less bugs and the more unit testing that is done on code the less bugs it will have.
Why reward sloppy behavior? Nothing wrong with getting developers to own it.
The project I subbed out was a fixed priced project. Bugs and omissions were plentiful, and although I wish the developers were more careful, at the end of the day it was their own time that they were expending on fixes.