There was a professor where I went to college who would do this too. He had his own freshman engineering "textbook" that he'd "update" every year and force his students to buy. It was legitimately the lowest quality textbook I had ever seen - it was as thick as a dictionary but only because the font was huge, the "covers" were just thicker paper, and it was full of spelling/grammatical errors as well as technical ones about the subject matter. His "updates" were always minor restructuring of text rather than any actual improvements too.
FYI for any current students or parents of students: check the library for textbooks before doing anything else. Even if they don't have it, most universities have a system to check out books from other libraries that are "in network". I learned about this after my freshman year and didn't pay a dime for textbooks the rest of my time in school.
bonus crypto complaint: it's really sad to imagine crypto/blockchain tech being used to force students (or anyone) to pay for library books.
One of my college biology professors assigned his own textbook for the class, but in order to avoid a conflict of interest he refunded his royalty to any student who purchased a new copy.
FYI for any current students or parents of students: check the library for textbooks before doing anything else. Even if they don't have it, most universities have a system to check out books from other libraries that are "in network". I learned about this after my freshman year and didn't pay a dime for textbooks the rest of my time in school.
bonus crypto complaint: it's really sad to imagine crypto/blockchain tech being used to force students (or anyone) to pay for library books.