The way it's been explained to me is that it's proportional to how much money you're spending. If you think you're getting a great deal from the Chinese, then the Chinese think it's reasonable to rip you off.
Whereas a manufacture in another country might say: "For that little money, I won't do the job.", in China the answer is more like "For that little money, I'll do the job [but I'm going to rip you off, and for how little you're paying, you should already know you're going to get ripped off.]"
Unfortunately I don't have more details; it's something I heard a few years ago from a Chinese coworker. He was explaining that quality products can be produced in China, but you have to pay for that quality just like anywhere else. And it happens that when American companies outsource to China, they're often looking for the cheapest bidder.
Whereas a manufacture in another country might say: "For that little money, I won't do the job.", in China the answer is more like "For that little money, I'll do the job [but I'm going to rip you off, and for how little you're paying, you should already know you're going to get ripped off.]"