Is the purpose of the textbook for problem sets, or as reference? In either case, previous editions are often much less expensive than the most modern edition (

Is the purpose of the textbook for problem sets, or as reference? In either case, previous editions are often much less expensive than the most modern edition (sometimes the professor already owns the previous edition too). But if the purpose of the textbook isn't for the problem sets, then there are likely inexpensive or free (by author or by copyright expiration) books that are fine for the other purpose. (I have a liking for Schaum's Outlines that cover a nice spread of topics.) I'd add that if cheating is a concern (whether from using books whose solution set is easily available, or using in-house solution sets that don't update with each year), then assign watching a previously recorded lecture (by the professor, or one of the excellent already available ones online) as homework, and use the in-class time to have quizzes, tests, or professor-assisted homework sessions. In addition to weeding out cheaters there's the benefit, if you believe Salman Khan, that such methods are probably better ways to learn the material. Finally, it's not too time-consuming for a professor to scan the problem sets from the book and distribute them to the students. So long as the problems aren't highly specific to the text, the student ought to be able to solve them without the text. For many subjects there are lots of free resources out there to learn from.