I'd walk on the dealer's offer use lease compare and anyone else to get better terms then walk in and get the car outright for the price you wanted and tell him exactly WHY you did it and that you're going to tell all you know about his practicies and that he get a clue next time he tries to run "game" like that on an informed buyer. Of course would do it after I'd paid for the car via lease compare.com!
'12 F10 550i (DGM-II - Dinan Stage 4/Intercoolers & Shockware, H&R Springs, Eisenmann Race Exhaust, Hamman CF rear difuser, Giovanni "Lindo" Graphite 20")
'10 e71 X6 35iDrive SAV (Space Gray) - Gone
'06 e85 Z4 M Roadster (Black Metallic) -Gone
'08 e92 M3 coupe (Sparkling Graphite) -Gone