The 91-92 camber setting is extremely aggressive (toe out) and designed for driving the car rather hard, so if you don't (and most people don't, even those who think they do), they can wear down the insides in 5k miles or less. 93+ camber is not so bad. I have had to replace the rears already, but they weren't new when I bought it and I have put over 5k on it since I bought it.
Tires cost the same as other tires do, given their size and performance. You can spend $100 or less or $300 or more. My rears were $170 each.