They charge depending on the size, but at least a few hundred dollars. Try tent/party rental stores, I think they have this stuff.
I got lucky, my caterer is taking care of it for me. I think we are paying $600 or $700 (can't remember) but I don't have to deal with it at all. I think you can get them cheaper though if you handle it yourself (of course, there could be delivery and set up fees).