Honestly, I think that anyone who is valuing it more than a couple grand isn't actually legitimately interested in the game enough to put cash on the table and is just throwing out random numbers.
1) Yes, it's rare, but as dung said, rarity != $$
2) It's game plan. It's not a particularly popular manufacturer to begin with. Imagine someone trying to sell an equally rare game from Bell Games or Playmatic or something.
3) It's non-working. From a manufacturer with low popularity. And hard to find parts.
4) It's not a popular/mythical title that people talk about, unlike Loch Ness Monster or Cyclopes. A game with the right theme, layout, and artwork can fetch a considerable sum. A game that doesn't have those things, not so much. I've had to face the reality with the rare games I've owned that don't tick all those boxes, which can make it tough to sell them.
So, you'll have to find someone who finds the rarity desirable, isn't afraid to tackle repairs on this type of game, and who might be interested in the gameplay/layout/artwork.
It would be easier to sell if it was working, and if there was a gameplay video available. Buying a rare game blind without seeing what it can do, how it plays, and what the code is like can drastically affect the price.
In order to get a significant price, a potential buyer is going to have to be interested in several aspects of the game.
Would I throw $500 at it? Sure, for me, it's a no-brainer. I don't mind tinkering with rare games, games without documentation, or game plan games. $1000? Maybe. $1500+, probably not--just because I don't tick all of the boxes for this game. I find the rarity and history of the game interesting, but artwork and layout don't really seem too interesting to me (or rather, enough to spend a considerable sum on it, anyway).
Would someone else be legitimately willing to put a significant cash sum on the table right now in order to beat out every one else to it? I have no idea. But judging from the responses in this thread, the interest level is lukewarm at best.
In any case, it is a cool find.