Thanks, but this is what they have on the Chinese Embassy website - sounds like more money more money :
20. I get a new passport, but I have a valid Chinese visa in my old passport. Can I travel with both passports to China without applying for a new visa?
Answer: It is not necessary to travel with two passports. If your passport has expired or is going to expire in 6 months or less, you should apply for a new visa with your new passport.