That is very surprising if it was a 2015 Mustang. FORD reimburses the dealers when people use the X-Plan - customer gives special issued number to dealer. It would be very surprising to see a dealer reducing the price that much, by themselves, on a new Mustang. Maybe on a 2014?
My local dealer is already doing 4-6k off 2015 GT Premiums. After the small print, it comes to 3-5k+ off depending how the car is optioned.
2012 GT Premium, Brembo PP, MT82, 3.73s, Blk/Blk. Bama 93R, Koni Yellow Rear Shocks, Hawk Ceramic pads, Luxurious & Plush Floor Mats