I think it really comes down to WHY you want this sled
I mean, IMO, and no bash here, its Not a real special sled, by any means,
its old school ride more or less, IMO, good for small riders, and NOT so much fun for adults , all the more so if they have any back or knee issue's!
F7's have a following and a ton of things can be done to them,. but the F6's, were nothing that built a big following
I Sold a 1998 T cat, with a full rebuild to better than new(AGLT front end, Crossfire 136 skid) with 1300 original miles on it
and got $3600, but the T cats have again a long following to them, to make them worth over book value!
NOW< if you have sentimental reasons for wanting this sled, then over book value is in YOUR eye's what you are willing to spent to have it
other wise, I really don't think many folks are willing to spend that much on this model sled, even in MINT condition, due to, well, its outdated, and even the low miles and appearance it has,
things can and odds are still need replacing, seals, bearings, all can go by from age alone
typically after you BUY a older ??what ever, and get it, and start to go over it, you FIND many things that are BAD from age!
SO< for me, personally, BOOK value would be MAX I'd even think about doing, unless I had personal reasons to go higher, and odds are I wouldnt; even pay BOOK value for outdated tech and ride quality!
My back and knee's just wouldn;t allow me to enjoy it !