You are being had
You can buy a rebuilt PS pump at fastlane (top of page) for about $320
You should get 2-3 sets of pads out of a rotor, unless you had some horribly wrong pads or the rotors are warped. Anyway, I just had the front pads and rotors on mine. Labor was $160 and I bought the parts here....
'00 ML320 "Casper"
'92 400E "Stella"