Many of the things are easier to check than to do. And where it isn't, you can have multiple people do the same thing.

And last of all: if you build a working relationship with the guys who do good work you can use them for more work.

I'd be worried that multiple rounds of feedback back and forth would cost more time and money than doing it myself.

Having multiple people do the same thing, and finding people who are quality-oriented and trying to stick to them sounds clever, though.

I never really give feedback. I either keep on or end contracts but I never attempt to coach them into being useful. The cost/benefit isn't there, as you pointed out.

Sometimes, it's just that the question isn't suitable for this method and I just sink the project till I can think of better.