In my first year, our chemistry and physics professors both authored their own textbooks for their courses. It was in the days before copyleft and open source,

In my first year, our chemistry and physics professors both authored their own textbooks for their courses. It was in the days before copyleft and open source, but the physics prof ran a print shop in his backyard, hand-bound the textbooks and sold them to us at cost (which was about 10% of similar published books). The chemistry prof, in contrast, contracted with a publishing house, and made sure to make a few changes every year, including re-numbering the exercises to discourage buying and selling of old textbooks. The (expensive) textbooks came with accompanying lab-books, which cost almost as much as the textbooks themselves. Lab assignments were only accepted on pages torn out from the official lab books.