That’s the kicker. You can’t even sell them back or sell them on ebay because they make minor changes and change the “edition” every couple years. A lot of these books are in their 8th or 9th edition, with little changed.
Occasionally, my kid has had a prof who said, get any edition of the book, so then the students can go on ebay and buy a really cheap previous edition.
A lot of professors pad their salaries by writing a “book”, which is their lesson plan, getting it published, then requiring the students to use it. The book that would cost $5-10 at the copy shop now costs $110, with the professor making a nice profit.
No BS, actually seen it at the local universities.