Sounds fair. They cant sell it for a whole lot more than that as brand new ones are going for just a few grand more OTD.
I remember your post last year, when you bought the 2014. Folks were criticizing you for paying too much for your car. The hit you're going to take is now going to be $8-10K instead of $4-6K if you had held out for a better price.
Hopefully, you have better luck with the 2015.
2011 Mustang GT M6 3.31s
Matt HONEYCUTT Tune, Lethal Off-Road X, GT500 axlebacks, J&M LCAs, UPR UCA, Whiteline LCA relocation brackets, Eibach Pro-Kit Springs, Koni STR.T shocks/struts, GT500 strut mounts, SR Strut Tower Brace
Best 1/4 E/T (05/18/14 MIR - no tune, X-pipe, or UCA): 12.920 @ 109.40 mph (2.059 60ft)