Not sure where you're buying rotors or having rotors turned but it's definitely cheaper to turn most. O'Reilly charges $15 per rotor and you ain't buying a rotor for that price. I don't turn them because a) you have to stop the brake job and wait a couple of hours while they turn them and b) you could end up taking them, they tell you they're too thin to turn (I suppose you could measure them yourself before), then you have to buy rotors locally and pay a LOT more or leave the vehicle until replacement rotors arrive.