Prices do vary a lot across the country, so it might help to ask other longarmers in your area what they are charging. Also, check to be sure that you are charging enough to pay for any and all taxes that you may incur. These can be substantial - for instance, if you earn over $400, you will have to pay social security and medicare tax, which is 13.3%. In some areas you may have to pay sales tax, business license, etc. You really are in a business, even if doing it for fun, and it would hurt to find out about all those taxes the hard way - after the customers have already been charged too low a price and the government still wants its money!
Funny, Bobbielinks and I were thinking along the same lines as I was writing this.