I really depends on the shop...around here it can be anywhere from 120-300. I got my wagon done at a place by my brothes work called Contour Tinting. They will go as dark as you want, and offer a lifetime warrenty against bubbling, peeling, fading ect..It cost me 240..but than again I have 9 windows.. I'm going to go back and get my front windows darker and have them add an eye brow.
Tinting makes a huge difference in how the car looks and helps a lot in the summer to keep some heat out and protects your interior from harmful, fading UV rays.