What are the statistics on this? There are about 500k professors in the US, and they make up about 1/3 of college teachers. Also, most academics would object to this situation, so it's not apparently OK. There's a growing movement towards open-sourcing textbooks or replacing them with other kinds of online materials.

Don't get me wrong, I think that college education is due for reform.

There are examples of finding better ways to do it. My son's textbook costs were very low. The regional state university that he attended had some kind of thing where you rented your textbooks and turned them back in, often with a nominal or zero fee.

One professor at my poorly subsidized state uni who had a book he required for class was $180 or so. He had enough (spiral bound Xeroxed) copies in the library for everyone to borrow for the semester. Or you could buy a shiny new one from the bookstore or online at full fare. Another gave the classes copies of the chapters.