What sort of cost is it to hire a celebrity to do a concert?

It really depends on who it is and how in demand they still are. When I was with Little River Band about 9 years ago, they were still getting 35000 dollars a night and hadn't had a hit record since the eighties. By the same token there are other acts from the same era working for 12000 dollars a night. Your best bet is to figure who you might want, go to the website and contact their booking agent. Be prepared, they get requests for pricing all the time from non serious people and will probably question you before they give you a figure. Good luck.