It certainly seems that scarce and rare get overused to the point of us wanting to gloss over them, and often rightfully so. I do think there's also the occasional exception of false commonality created by eBay listings on occasion, though. I'm thinking of Jughead's Folly, a 1957 one-shot, for example. Seems like no one wants it anymore, and there's maybe eight on eBay the last time I looked. But that might be about half of all of them. Of course, this is the exception rather than the rule, but I think some less popular older books may be truly scarce yet available in small handfuls at one time.