more like they are lucky to find any vendors who will put up with their harrassment , low paying fees and unrealistic demands! 

I have worked off and on for them for years (ATM/Servicelink) and they come and go..they find another vendor when they run you into the ground, then they find a problem with that vendor and start sending you work again....LOL...like I said, it is very frustrating when you know you are doing the best you can do and it is never good enough.  Hang in there..as you said your bottom line hasn't really suffered and your frustration level has greatly decreased.!...life is too short....!