The problem for text book publishers is that their system is not only very profitable, it's also easily replaceable. Calculus hasn’t changed much since Newton and Leibniz invented it in the 17th century. Yet there have been seven editions of James Stewart’s best-selling Calculus (list: $245.95), the profits from which allowed Stewart to build a $24 million home with its own concert hall.
So it’s not surprising that textbook publishers have filed the equivalent of the Recording Industry Association of America’s infamous lawsuit against the first MP3 music player. That’s what you do when your rents are threatened: use them to hire good lawyers.