I just got one of the new 2 year multiple entry business visa (F visa) good for unlimited stays up to 90 days per stay. It cost me $150 (plus visa service company fees). I previously had a 3 month (2 visit) visa and a 1 year multiple visit visa. The 1 year visa also cost me $150 IIRC. I went thru www.expressvisa.com as a visa service. I was happy with them, they were really quick. Although it's not like they do much. They just drop off your passport, pick it up and send it back to you. But you do have to use a visa service nowadays (if you don't live near a Consulate or the Embassy) since as of about a year ago the Chinese Consulates/Embassy stopped accepted mail order visas. I found out all the rules + good info that I used for my visa application at:
losangeles.china-consulate.org

Good luck and I'd suggest you get as long a visa as possible if you plan on going back more than once since its a pain to get a new visa every few months or every year or whatever.