All good comments so far. China is cheap, but hugely a function of how posh do you need to have a trip. If you want to go real budget (I often do), here's how I'd budget a trip to China (say 2 weeks):

1. Flight - good ticket is around $1K, excellent if you can find for less than $800 (recent deals around $550)
2. Visa - work does this for me, but I think tourist is around $175 after all fees (shipping, processing etc)
3. Hotels - if you're willing to go cheap and go local (say hostel style), you can find good accommodations in Beijing/Shanghai for say $25/night including breakfast.
4. Food (and water) - if you're willing to eat local, then you can easily spend less than $5/day (esp if hotels include breakfast). You don't need Chinese if you're willing to point, and obviously most street vendors you know what you get (i.e. fruit shops, etc).
5. Transportation - widely variable, with buses and subway being the cheapest. Walking is free but only short distances. If touring, maybe $10/day.
6. Souveniurs - I don't buy stuff, just take pictures, so for me quite free. But likely will want to buy gifts for friends.