If I asked you if you had a heart problem would you be willing to let someone kill you, cut your heart out of your chest, put someone elses heart in, and bring you back to life, would you say no because that seems SO HARD to do? No,
lol...wherever do you get your examples from?

Let's say it wasn't $20 but more like $200 minimum, and I'm just talking a quote price- the time it would take for an advanced do-it-all coder to look at someones code and make an estimation of how long it would take them to rewrite everything. One blot on the horizon I can see straight away is the spaghetti factor involved when it comes to games, in other words there is much more that goes into games than just code. As Squize has mentioned, a noobie coder might use oversized bitmaps images, vectors, animations that don't fit the framerate- who knows. There's that and a million other tweaks to get the gameplay just right. Maybe he wants you to optimise his code to AS3 when it's been written in AS1 (total overhaul).

Game-coders are the unhailed neurosurgeons of the programming industry, you'll understand that once you investigate more carefully the scope of how much actually goes into a professional game. Most complete game coders who can do anything are guys who were programming when they were six. You would have to find a suitable payscale to match such experience.

It's not such a crazy idea within a framework. I get dozens of mails about tutorials I've written and because- like Render said- the framework was already in place (I designed it) for me knowing what is wrong with their code and how to fix it quickly is relatively simple since I wrote the original code they have manipulated. So say you had a similar person employed as full-time staff and their daily job is fixing games that were built from his own template/s, ie a support for guys in different industries who build a game from your own with maybe a couple of small extras thrown in and unique graphics of their own THEN it might not be such a mad idea to facilitate.

But...a free-for-all service where anyone can just pass along their game and have it completely revamped to a professional level? That's quite unrealistic at a cheap price. In most cases there's no difference between that and someone just coming along and asking you to design a game from scratch.