Textbooks, on the other hand... https://en.wikipedia.org/wiki/Textbook#Market https://en.wikipedia.org/wiki/Textbook#Market > In the United States, the larges

Textbooks, on the other hand... https://en.wikipedia.org/wiki/Textbook#Market https://en.wikipedia.org/wiki/Textbook#Market > In the United States, the largest textbook publishers are [four companies]. Together they control 90% of market revenue > Harvard economics chair James K. Stock has stated that new editions are often not about significant improvements to the content. "New editions are to a considerable extent simply another tool used by publishers and textbook authors to maintain their revenue stream, that is, to keep up prices." > the primary factor contributing to increases in the price of textbooks has been the increased investment publishers have made in [bundled supplements e.g. one-time-use codes for a website] [...] the publishers' practice of packaging supplements with a textbook to sell as one unit limits the opportunity students have to purchase less expensive used books