The argument in publishing industry (about papers and textbooks) is that if you cannot afford to buy/rent at the current market value then you still can use a public/university library to get it. This became actually more of a cliché than an argument over time. Now with a significant portion of textbooks (and books in general) become mainly E-books, the industry limited library capabilities and required pay per lend…
I don't know about textbooks, but the overall share of publishing industry revenue that comes from ebooks is really low. Something like 7%, and falling steadily. I had assumed it was much larger.