Rare means that aren't many to be had, seldom encountered. Now if no one is interested in the item, that doesn't make it less rare, just less desirable. So does that always mean that rare = expensive? Cost is determined first by demand, and then supply. Do you want something just because there aren't many available? Does the item become more desirable when there are fewer of them? "The girls all get prettier at closing time", but that doesn't make the hairy lady from the side show any less rare.

Just couldn't let everyone else talk without putting my 2 mils in.
Dave