Makes complete sense since the Rotor is just a hunk of iron that is a heat sink which dissipates heat generated by the friction between it and the pad. So as you machine off that bit or bunch of mass and then go ahead and subject them to track speeds, heat and conditions you will eventually over tax the stock system be it the rotor then eventally the fluid in the calipers and unfortunately eventually you'll get a soft to mushy pedal and ultimately you'd lost braking ability altogether.

It's not a fun experience, been there did that a couple of times myself.

 

900 bucks!!!!!!!!!!!!!!!!!! OMG that's wild man...better to get after market pads and get the pads resurfaced elsewhere...