[Exhibitman]

If it is that scarce how do you even know it is overpriced? If there is enough of a recent history of sales to analyze and determine that the item is overpriced then it isn't scarce.

I run across this all of the time with the stuff I like to collect. How do you evaluate a team-issued card or piece of stadiana that no one has seen before, other than at auction?

You can't distract yourself with 'what if' questions. Odds are your item is not unique and odds are another one will surface. Some day. Maybe. But you can't control that. And even if there is another one for sale next week, so what? So there will then be two of them. They are still scarce.

What the other guys said goes: if you want it and can afford it, go for it.