Tint shops vary in price from one area to the next.
I would ask around, don't just ask about price, ask about the quality of the tinting materials they use.
A great price means nothing if you have to have the job done twice to be happy with the results.
Also know the laws in your state, some states don't allow very dark tints on the forward side windows.
For instance deep tints would be allowed behind the drivers view, but not on the drivers or passengers doors, most states don't allow any on windshields at all.
My car came with dark windows, the rear doors, quarter windows and the rear glass they are very dark privacy glass, I really don't think it helps keep the car cool, but it does look cool.