>Assuming these texts exist in large quantities seems to definitionally contradict the term
rare book. Plenty of books have small print runs or have reached out of print status.
They're books that are no longer in print. Doesn't mean there aren't a lot of copies around.
>Ultimately, you don't know how big N is, and that's what matters. Part of the problem is there is no transparency around this. The population of all books != the population of a specific book or set of books. Assuming N is large when you have basically zero information on specifics is foolish. These books might be just as rare as a film for which only one source exists you don't know.
All of this is frankly irrelevant. Books that you buy in bulk at barging bin prices are books that have essentially no market value and were going to the pulp or landfill anyway. Nobody has an obligation to spend money to preserve every extant copy of every book forever. Millions of books are destroyed everyday. Even libraries and archives make these choices. I was simply pointing out the film analogy worked better, but it doesn't change anything.