Thats hilarious, It might be a out of production thing I upgraded to the 335is mount long time ago on my N52 330i and I paid less then 100 for the genuine BMW mount.
Edit, if you see my post here
http://www.e90post.com/forums/showthread.php?t=881816
You will see that I paid 78 bucks for the genuine 335is mount LOL.