doesnt surprise me at all that it cost that much, especially since all dealerships charge more than $100/hour for labor.
you can always come to our next DIY at Martins Motorsport. its not more than a 20 min job and most of that time is waiting for the oil to completely drain. you'd probably save about $60 if you DIY
http://www.nccbmwcca.org/index.php?id=156,1185,0,0,1,0