The worst offenders are the professors who write their own textbooks (even though there are dozens of better ones already available) and then use them in their courses, making money off each student.
I think you are seriously overestimating the financial gains such a professor would make. I've taken several classes with profs who teach from their own textbook; the profit per book sold that a prof receives is usually minimal (either because the book is sold for near cost or because the publisher takes most of the profit). In fact, most such textbooks (essentially just rigorous lecture notes) are downloadable for free anyway.
If you want to make extra money as a professor, writing a textbook and then forcing it on a single class of students is about the least effective money-making scheme I can think of.
I think you are seriously overestimating the financial gains such a professor would make. I've taken several classes with profs who teach from their own textbook; the profit per book sold that a prof receives is usually minimal (either because the book is sold for near cost or because the publisher takes most of the profit). In fact, most such textbooks (essentially just rigorous lecture notes) are downloadable for free anyway.
If you want to make extra money as a professor, writing a textbook and then forcing it on a single class of students is about the least effective money-making scheme I can think of.