It just isn't feasable to do a window swap. The rear glass is the most expensive piece on your car. It lists for $1500, but has it for $1300 at www.fordparts4u.com. I good tint job is $150-$250. If your not used to handling glass(it is much heavier than it looks), you WILL crack it or shatter it. Try learning to tint yourself if you much have the satisfation of doing a job yourself. BTW, tint isn't priced out by the % of light transmission. A majority of the price you pay is for labor. A small portion maybe $20-50 is the cost of the tint itself.
If you want to learn alot about tinting try tintdude.com
If you want to learn alot about tinting try tintdude.com