In fairness, as a philosophy major, I realized fairly early on that most of what we read was out of copyright. I suppose if he's assigning stuff that is ABOUT what some philosophers wrote, it makes sense, but forgive me if I prefer just saving money to read Aristotle from Project Gutenberg.

And sure, there is more contemporary philosophy, and it's great he's keeping the books affordable. But if it's anything early 20th century or prior, don't be so surprised people are going to read what's in the public domain instead.