I have had a lot of experience in shanghai with KTV, usually with a local. Pay for the room, depends on the quality of the KTV and size of room, generally a room will cost Rmb 600-1000 depending on location of KTV, and type of room and quality.
They usually include 10-12 beers, Heinekin or budweiser. You pay Rmb 2-300 for the Mammasan and the girl serving drinks - each. Pay the girl sitting with you Rmb 300, as you will be a foreigner. If you take her out, the payment of Rmb 2-300 becomes part of the deal. Expect to pay Rmb 800-1500 depending on the girl in Shanghai.
It is great fun, especially if you have several people with you.