Given my limited experience of choosing a MKVI, and from players I know, £3,500 to £4,500 is typical for a well set-up and great sounding VI. They are in demand. People go more for the sound than cosmetic condition and often the ones that have weathered less well have done so because they're good and so have been well played and well used. I chose the worst looking of the 3 I tried, and it sounded really special where the others weren't as much so. It cost a £1000 more than the cheapest (and best looking of the 3). I would have been delighted if it was the best looking too. It's not necessarily a bargain if one comes up for £2k and it can be a waste of money if the sax is nothing special.
I wouldn't disregard, or call a gimmick, something with a difference, it would be all about how it played and sounded.