I just wanted to say that this price-gouging is most egregious in the legal world, where the textbooks are full of case-law that is legally required to be freely available. The prof's add their notes at the end of each case and then sell the book for $200. They could simply give you a link to cases & a little pamphlet with their notes.

What bothers me most about this whole setup is it makes a legal education even more expensive than it already is for lower to mid-income students.