There's actually a long tradition of this kind of thing. As an undergraduate, my first-year maths "course notes" were actually a textbook in all but name, prod

There's actually a long tradition of this kind of thing. As an undergraduate, my first-year maths "course notes" were actually a textbook in all but name, produced by the Mathematics department and sold for a very modest cost, bypassing the publishers and the campus bookshop because the markups by both were outrageous Even if you'd paid the authors $10 per copy it would have been a bargain.