Most textbook authors make a pittance. A few make it big if the book is a widely adopted perennial best-seller, but that’s a tiny fraction of all the textbooks published. I’d guess that most textbook publishers barely break even on many of the titles they publish, even at those high prices, simply because the market is relatively small and their fixed costs are relatively high. They make up for it on volume sales of the most widely adopted books. The “racket,” in my opinion, isn’t the royalties that textbook authors receive, but rather the publishers’ practice of putting out a new edition every few years, even if there’s not that much new in the field. This is done for the express purpose of killing the after-market in used books, for which the publisher and author receive nothing.