Because YiFu doesn't deal directly with TMSC, he deals with someone that deals with someone that deals with someone else. He probably pays three times what they actually cost from the fab, and someone else in the process makes sure that twice as many chips get produced, etc...
I remember he told on a video that one must know people (have personal contacts) in China to make business. Now it turns out that he actually doesn't. Instead, he knows people who know people who know people.