[jacobreg]

On the other hand I had a professor who wrote a book just to teach this particular course, and sold it for $5. It was a great text and a great course.

[bb88]

He probably made money on it (even if it was $100). I've heard of profs writing books explicitly for their classes and not making money on them.

[rusticpenn]

The money required to print it probably...

[yummypaint]

All the prof-authored material ive seen has always been provided as a free pdf before the course started. There is really no excuse for not doing this in 2019.