For any new BMW, whether specifically ordered to be made, or selected from the dealer's inventory, you are better off negotiating an amount over invoice, rather than using the MSRP as a starting point. It varies by vehicle and by geographic region, but you should be able to negotiate a new 2013 X6 for $1000 (give or take) over invoice. There is approximately a 7.5% spread between MSRP and invoice. Hope this helps.
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