My view is that this would be unethical if the professor profited from sales of the notes to the students, but not otherwise. I've done this sort of thing myself, writing an extensive set of notes for an important course and having the university sell it at the cost of duplication.
The reason that it was important to do it this way was that I needed to quickly refer to the notes by page (and line) number for certain discussions. It also made it possible for students to use the printed notes as a means of keeping their own notes, by annotating the printed version. But I never "earned" anything from the sale.
While it wasn't "required" in the sense that you were forbidden to take the course if you didn't have a copy, it was essential enough and referred to often enough that the students got their money's worth.
My opinion also, is that if a professor requires a book that s/he wrote in a course, then the professor should refund to the students any net revenue that they receive from the sale. Usually a $90 textbook would yield around $5 or so to the author(s). But, if no revenue to the prof occurs, then this case doesn't apply.