I've found that if you've not been able to find something you sorely wanted for years and you don't jump when the opportunity arises you'll face years of regret.
Several? SEVERAL years ago?Several years ago I found a like NIB 6" blue Snake for $750.00. This was a little over what I'd seen other Pythons for but ,since it was in such good shape,I bit the bullet and paid up.
Say there is a rare gun you have wanted for a long time. (think years) You finally found one available at a steep price.
My thoughts at this point is there is nothing to say. We can talk in vague terms or you can, but we have no idea what your definition of overpay is and what kind of a firearm are you talking about. For that matter, I own rare or certainly low production guns... but you should define "rare".