What's the premium for it being a Bullitt and having 2,700 miles? What would a 10-30K V8 Mustang that's about 10 years old be worth normally?
Looking at eBay completed listings, it looks like $22,500 for this one was just under market value. Normal ones with 3-20K miles sold for $16-17K. Based on that, I'd rate this one a buy. Not too much of a premium for a somewhat special edition with some bona-fide upgrades. Looking at TrueCar for a lightly-equipped 2018 shows them going for about $33K or so. A lot more car for the money there, I think. Mustangs have always been a lot of car for the money. I think I paid $16,800 for a loaded 1989 5.0 LX Sport Convertible.
I think for a few thousand more, I'd get a Boss 302 or Shelby GT500. Probably more upside potential down the road...
https://bringatrailer.com/ford/mustang-s197-2005-2014/