F10 M Sports hold their values very well. I know because shopping for 2011 535i M Sports showed pricing that was similar to Dealer discounts applied on brand new 2013 M Sports.
Hopefully this doesn't change as the M Sport Packages are more accessible on the 2012 and now more-so on the 2013 models.
'13 F10 BMW 535i Sport
: Jet Black/Black-Anthracite : Premium & Technology Packs/Sport Auto Trans/Camera/Park Distance Control/Heated Seats/Tinted Windows/Blacked Out Markers/Performance Spoiler.
Ordered: Porsche Macan S / SportDesign.
Ex M-B's: '11/'10/'06 E350 "Sport", '02 S500 w/ Every Option.