Unless the calipers are leaking, they do not need to be replaced. 600 is a fair price if all this work was necessary, but I don't beleive that it is. Make sure they're not leaking and the sliders are moving freely, slap a set of pads on it and machine or replace the rotors. You'll be into it for $150-$200 and If you use good pads, it won't squeek.
