Extras. You may get $10.00 an hour at a restaraunt, but also you get $50.00 extra every night you don't get a complaint lodged against you. If an actor gets to keep the costume they used in a movie...
The word "perks" when used in phrases such as "the perks of" usually means "the good things about" So you could say that the title says "the good things about being a wallflower"