Hi,
For that price, I can't imagine they actually changed the Rotors, at list price, the Pads and Rotors total $668 alone (and that's an old Price List). They're correct that you cannot machine the drilled Rotors, too difficult for the lathe and greatly increases the risk of cracking.
As stated, 2-3 Pad changes per Rotor change, a little more like 2 would be the norm. A Pad change at 18,800mi. indicates pretty severe use, even for just City driving. They should go closer to 30k-35k mi., but everybody's driving style differs.
Glad they only took the Arm and left the Leg...
Happy Motoring!... Jim'99