Everyone in academia knows it: textbook publishers abuse the system. Jim Fiore decries the high cost of college textbooks, and I have to agree completely. Basic textbooks at the lower undergraduate levels do not need a new edition every year or two, not even in rapidly changing fields like biology.
Churning editions is just a way for the publisher to suck more money out of a captive audience. It makes it difficult for students to sell off their used textbooks, it gives faculty the headache of having to constantly update their assignments, and if you allow your students to use older editions, it means we have to maintain multiple assignments. It’s extraordinarily annoying, and to no good purpose at the university (to great purpose at the publisher, though).
Right now, I do tell my students that I allow them to use the current or the past two editions. I also tell them where they can pick up copies online, and I even encourage them to get them used. I am doing my best to subvert the publisher’s evil schemes.
On the plus side of their ledgers, though, I also urge the students to keep their textbooks once the course is over. These are valuable reference books that they may well find handy throughout their college careers and in their life afterwards. I’ve never quite understood the rush to dispose of those books the instant the semester ends — I kept my undergraduate biology and chemistry books until they fell apart (another gripe: the increasingly cheap bindings of these books), and I still have several of my old history texts on my shelves.