You have some options here if you're on the floor with this price.
You can go aftermarket, using non active ones and use defeater plugs so that they do not throw faults (these will not cause a CEL, but only fault codes, I think). I think that the reason for the active mounts is to dampen vibration at idle.
See here.
http://www.rs6.com/showthread.php/23...-Numer-Request
I've just used an appropriate diameter of rubber tubing to slide over the post and provide enough friction to hold the cover in place.
I might have some of these laying around if you need them. I'm guessing that they're not that expensive though. I couldn't find a P/N for them in ETKA.