Roy's comments do make sense, but you can apply that to almost any car.
Someone with the means could save a lot money and turbocharge their "run-of-the-mill" 911 (amongst other mods) to build a discount 911 Turbo, but who the heck's gonna do that?
For me, the 5.0 2011 GT is probably in the sweet spot for bang-for-the-buck mustangs. V8, 400+ hp, $40k, RWD, looks cool, sounds insane, okay interior...sweet.
Beyond that is getting silly to me for a mustang, but I'm not headed to drag races, nor am I baby boomer with cash to burn. I could absolutely see the draw for some to buy this beast rather than Boxster/E Class/loaded 335i/etc like all their 'pansy' country club friends...
Especially if you've already got an E class in the garage.