I went to a private school and got my dress made for me, it was about $800, shoes were $500, bag, hair, makeup...I don't even know how much, tickets were $150 each.
We had an afterball at one of our classmates houses, she hired a band, waiters, bouncers etc. Her parents paid for the people living around them to stay in hotels for the night, so we got crazy drunk and loud and were still partying at 10am. It was really really awesome; totally worth all the money (which I had to pay for myself)