Are you referring to those China Mainland mathematics books that are usually published by those big universities in Mainland China?
Or those textbook in English but printed in Mainland?(much cheaper than the standard version, but lower quality)
Personally I got 2 books like that(in English, but printed in Mainland China)
I bought Rudin's Principle of Mathematical Analysis for around 5 bucks new.
Then again, I am pursuing my study in Hong Kong, so it's easier for me to get those books.