We have rented the gym on 2 occasions, ours is $100 for 2 hours. That gives 1-1 1/2 hours of instruction with the owner and 30 minutes to 1 hour for cake, foods, and opening gifts.
I find that all the little stuff adds up very quickly. Plates, cups, napkins, hats, all that stuff isn't free so the gym providing it is good. He sets up the tables, put the table clothes on, decorates a bit with the same colors if he has the right ones, takes down, cleans up the tables, and mops up the spills, etc...that is worth a lot in my book.
I think for a fun party that is something different than just getting together for cake and ice cream at the park this is the way to go. I don't provide any other food than cake and perhaps ice cream. It's a birthday party not a meal. I don't do goody bags either, I refuse to give kids a present for coming to a party.