Now $2500 would've been way too cheap for parts/install/labor. That should've been your first clue that something wasn't adding up right.
Paint shouldn't have cost more than $1200. Labor is relatively easy, but body shops will charge an arm and leg for it. Definitely got ripped on this one, but not much you can do now but enjoy it.
They should also have a receipt breaking down paint/labor for you. That will tell where they really took advantage of you.