Where I work, we turn the brakes with a brake job, unless it will put the rotors at or below minimum spec.
If it passes a NVH test, then that means that turning rotors is just as good as replacing them. On my own car I usually get one turn and then replace the second time i do them.
And from my experience, the cheap rotors at the auto parts store can often be cheap, mass produced, and even warped off the shelf.
If it's 19 to turn or 30 to buy, I'd prolly just buy them.