In engineering school in the 1990s, a Taiwanese student in our school would order all the books in Taiwan and then their mom would ship a huge box to us in Canada. It costs 50% less than buying the same books in Canada. Textbooks are a racket.
That said, we weren't required to buy any books at all and and books we were required to read were kept at the library in the "core" section, so there'd always be a number in the building, not lent out. As it turned out, in retrospect, I don't think any specific book was ever actually "required" to be read.
I did buy a few books (about 10 over 4 years), including a copy of Stroud's Engineering Mathematics so old it recommended logarithm tables (otherwise it was perfectly serviceable). I bought those because I actually wanted them to keep and I still have nearly all of them.