Some universities take it a step further and include the cost of textbooks in tuition. Be glad that isn't happening globally. That's the worst case scenario here - students are just billed for course materials without having any say in the matter.
Note that their stats about how rentals save students $1160 a year are sort of BS. On books where renting saves you a lot of money over the full retail price (which no one ever pays anyway), you can usually just buy the book outright for the same amount on Amazon (and then sell it back when youre done for a ridiculously lower total cost of ownership).
Just come out with a new edition each year where you move the problems around so that people have to buy the new textbook and cannot buy used. And in the occasional case where that does not work, change the title of the book occasionally so that students do not know which second hand book to buy.