There was a kid who was stealing my lunch money during Gym in middle school.. $20/day
I paid 1 weeks worth of lunch money to the really big bully 2 grades above me to beat up the kid who was taking stuff from my locker.. (these lockers had metal mesh holes)..
The thief got REALLY hurt.. I somewhat regret it.. but when I think back... I probably did that kid a favor, out of pocket n' all.