I know exactly how you feel - been in that scenario many times over the years. But remember the dealer's body shop, or the body shop the dealer sends you to, will guarantee the work as long as you own the vehicle, and will repair and paint it per BMW specs. Down the road if and when you decide to sell you vehicle, the body and paint work done by an independent discount body shop today may impact the FMV. I would figure out the best angle to grind/negotiate with the dealer body shop. There is often a preferred body shop referral rate. See if you can get a 15-20% discount. On the estimate they gave you, look at the labor rate and estimated hours of labor - that's where the negotiation room is ....
2011 F10 550i Carbon Black M-Sport, Black Dakota Leather, Premium 2, Sport Auto Transmission, Split rear Seats.
2013 X6 3.5 Space Gray, Sand Beige Leather, Y-spoke wheels