What's "TB shape"? ThunderBird or Gumby? For the record the Gibson EB like double cutaway was only officially JetStar for a brief period so the vast majority of folks who are not consumed by an anal tendency towards precision (oh, a Fender joke) in language use JetStar to refer to the earlier bass that went out of production circa 1967 and JS for the later bass. I speak as someone who made a public fool of myself correcting someone who referred to a 1970's double cutaway model as "JetStar". Turns out they were right and there are even
some of that body style with a SD prefix in the serial number.
However, to answer your question,
this 1965 JetStar with 2x2 headstock was restored by a LTG member and it apparently failed to sell for $1,500. There's a shop in Germany that has been listing a canary yellow refin for over $1600 USD for two or three years. The year might matter since the (later) 4x1 headstock seems to be a bit more in demand. That's the model Peter Tork of the Monkees played.
Anyway, if you pulled the Bisonic you'd almost certainly get $500 (IMO) for it alone if you were patient and Dark Stars continue to remain difficult to get. So that, plus the non-sale, says $500 is a bargain and $1,500 is never gonna happen. Split the difference at $1000?