A colleague of mine, who teaches chemistry, claims that these days, sales of copies of college textbooks are no longer profitable for publishers. He says that their revenue is now from services, such as answer-checking services like MyMathLab. I asked him to provide a source for his claim, but he didn't. I have a pretty hard time believing this as stated, because his statements sound categorical and extreme. But is there at least some truth to this? Is there any way of knowing, since the publishers may not make the data available?
My suspicion is that a $280/copy o-chem text is even more profitable than it was before, because the online services can be used to force the students to give money to the publisher. Before the online services came along, a student could just buy a used book, which would put no money in the publisher's pocket. Now, the student may have no choice but to buy the book shrinkwrapped with a card providing access to the online service.
The publisher can also rent the book to students in electronic form, with a DRM scheme that makes the book evaporate after a year. This also helps to kill off the used book market.