i would say around £200 max for an impreza saloon for example.there is only 3 windows that can legally be tinted..even £200 is expensive for that car tho...on the side i would do that for about £100 with tint bought by customer...your best bet (if you have the front) would be to see one of the lads in a tint company if he would be interested in a bit of work on the side.