Rare != valuable. They are "betting" pennies in their books. Rarity equating monetary value is a common logical fallacy often found with stamps and other coll

Rare != valuable. They are "betting" pennies in their books. Rarity equating monetary value is a common logical fallacy often found with stamps and other collectable cultural artifacts (details would disgress too much here, see Pokemon cards or whatever). And rarity vs quality ir utility is even harder. But value is 1) not determined by scarcity and 2) neither by "unique information content" (because that's by definition not measurable without a panopticon) and 3) nor by "creative value" per se 4) it is indeterminate whether some detail in a work might prove useful later, in general. Even for scientific papers. They just can bet on all fronts and for training material it's 100% rational to do it. Apart from that, to briefly disgress into the discussion of "cultural value": many cultural works we hold as very important today were sold for cheap, if at all, when the author died. Music scores are good examples. But back to the broader "value"/rarity angle: The historical value of some odd self-help or DIY instructions book from the 80s is hard to determine! It might happen to be able to provide a secondary source for something, or even act as primary source for some other fact of the time that is tangential to its subject. None of the qualities that make trivial literature interesting to, for example, researchers, must correlate with market value (at the time of writing or at the time of research?). Sure, there are truckloads of "unique" books from even 200 years ago that are neither culturally valuable nor sellable right now. But these things can change quickly. Imagine you want research details about old retail products. Or the usual street price of something in some city at a specific time. Or the inhabitant of a certain rentable space at a certain time. Or some specific detail about replacing the parts of a certain type of car that's no longer around (is this valuable then?). Humans create endless complexities, and monetary or evolutionary value is not coupled anymore to step-changes such as "how to light a fire using X,Y,Z". We're deep down the rabbit-holes of our own ephemeral shaping of our world. What word was commonly used to describe a sandwich in 1925 in Hungary. Or what problems did people commonly encounter when repairing car doors in the 1940s in England? Whatever. I can't make up a good example right now, but market value does not imply quality; and even quality (according to some cultural norm) is not universally measurable.