Usually rotors are not warped... they get uneven deposits from the brake pad material which makes them feel warped. Turning the rotor (which grinds the surface smooth again) fixes this, but because it removes material you have to measure the rotor to make sure it still has minimum thickness.

Since I don't own a turning machine, I would've had to have a shop do it, which charges like $70+ per hour. It was cheaper for me to get $30/each Brembo blanks.

One thing for sure: you ALWAYS either need to turn the rotor, or get new ones as the rotor usually has mated to the pad (with pad deposits).

You could just slap new pads on, but you'd lose braking performance due to the unmated surfaces. Eventually they'd mate together, but you'd have a period where you'd have reduced, non-mated performance. Do it right.