I quite recently bought a used book for something like $100. Certain books can be expensive, it was not a popular or particularly good book, but the writer was a character and I guess therefore his written books are valuable niche items... Also no more will be printed, so there is limited supply. Similar for some old music sheets or records.
However these are definitely not liquid, if you are going to sell them you maybe have to store them for a long time.
Idk with the amount of books referenced and the definitive fact the some of them were resold at least indicates a good chance of making thousands of dollars, otherwise It’s logical to assume if the effort has not been worth it the author would have commented as such.
A lot of older books that are now out of print often run many hundreds of dollars, if not more. For example, I've been trying to find a complete unabridged edition of Fraser's Golden Bough, which isn't that niche - you'll find it cited somewhere in any work on mythology- and it seems to run in the high-hundreds to low thousands. A quick look shows a first edition selling for 12k all by itself.
Similarly, I'm looking for the complete Collected Works of Carl Jung, and that's got a hefty price too. Maybe one day. :)
I'm sure both of these examples are sitting in some old man's study and are getting sold for nothing at estate sales, if they aren't just thrown in a dumpster or pulped after being donated to a library that can't get rid of them either. But nobody is indexing estate sales.
But a pallet of old academic books is unlikely to be composed of such books. It is probable that most of the books are worth less than the cost of shipping, and some of the books will have some value but not tremendous value. It is astonishing the number of wonderful, high quality books that can be bought on Abebooks for $1.
Did you look at the picture? https://i.imgur.com/0qiTKSQ.jpg Books I commonly buy secondhand that look roughly like those pictured are anywhere from $10–$200 each (depending on how common the particular book/edition is); we’re talking about pretty ordinary old academic books, nothing fancy or extremely rare. A pallet of books is ~500–1000 books (there are maybe 400 in the picture, but the blog author claims that is a "sampling").
That's selection bias because you are only looking at books that you actually wanted. An average book is worth much less than a book that someone actually wants.
An average (~worthless) book is something like a pulp romance novel, political book by a sitting politician, self-help guide, .... These are printed in the millions and used copies can typically be found for $1–$5 + shipping costs. That’s not the same kind of books primarily shown/described here.
Any scholarly person who loves old hardback books and spends a few decades collecting ones they personally want or need is going to end up with some worthless books, a large number that sell for $10–50 each, and a few that are worth hundreds each. It’s just inevitable, unless they go out of their way to only collect junk.
If I had to guess I’d put the price of the old man’s collection in the $10k–$30k range. But it’s plausible it could be more, if he collected anything rare.
I have a book printed less than 5 years ago that routinely sells for $800 online now. The niche religious press that published it simply cannot keep all of the authors work in print and his more academic work gets printed maybe once a decade in a run of 1000.
The article said, "there were some very old, and often valuable, books in this boxes," which is somewhat difficult to interpret but seems to be saying that many of the books were valuable in the sense of fetching a high price, unlike those sold on the rather offensive page you link.
