1. I'm an English professor, not a lawyer, but doesn't "consider the least costly practices" mean something other than "requiring faculty members to choose"? (That's a genuine question for any lawyers who happen to be wandering by my blog.) "Please figure out the least expensive way of doing this" doesn't necessarily mean "you must choose the Dover Thrift Edition." Or does it?
2. I do wish the people using the Cancun defense for textbook selection--i.e., students are blowing their money on going to Cancun, not investing in textbooks--would stop, for the following reasons:
a) Many students are not going to Cancun on spring break, and yet are having a hard time affording textbooks. (When I was at UCI nearly twenty years ago, some administrator grumbled about students working so that they could buy TVs or whatever, even though at the time, undergrad living expenses there were ranked tenth highest in the nation. The students I knew usually weren't working to buy goodies; they were working to pay for room, board, and transportation.)
b) Even if a student blows $1100 on a trip to Cancun (that appears to be about the bargain rate), it does not necessarily follow that he or she also had to spend $1100 on textbooks for the semester.
3. Most of these regulations seem more applicable to folks in the STEM fields, although English professors run into textbook turnover with the major anthologies (although Norton and Longman don't issue new editions every year) and composition texts.
4. When I do the upper-division Victorian survey, I try to use electronic editions for the prose works, rather than having students purchase either a very expensive anthology or very expensive single-volume editions (of which they will be reading only snippets). But...most of these editions? Aren't really adequate for the purpose. Even a well-produced and proofread PDF file (like those here, for example) lacks stuff like, oh, introductory materials, footnotes, bibliographies... I can sacrifice headnotes and bibliographies, but the students need footnotes. At some point, I suppose that I'll just have to write them up myself.
5. I've noted an increasing number of students who just head on over to Amazon to buy secondhand copies. However, this is causing its own problems; the secondhand dealers are not always, shall we say, exact in describing editions, or listing books under the proper edition, which can occasionally result in angst. This is a problem when assigning Shakespeare or even Frankenstein, as editions can vary widely depending on the copytext.
6. Electronic editions come with their own hidden expenses: do campuses charge for printing? Even if the student has his or her own printer, how much would they have to spend on ink or laser cartridges? Does the student have a laptop to bring to class? If the instructor wants to make things simpler for the students, does s/he have easy access to a smart cart or something else with a projector?