I haven't paid for anything in a long time, but the dumbest thing I ever SAW somebody pay for was flat repair. A friend who owns a popular shop here puts on a nearly full-time employee for a few weeks in spring to do minor fixes on bikes that sat over the winter. He lubes chains, adjust derailleurs, stuff like that--but he spends about half his time replacing tubes (they don't do patches). I think he charges $7 plus the tube. It's inconceivable to me that anyone would ride without knowing how to fix a flat.