According to David Bollier, CalTech professor R. Preston McAfee turned down a massive advance fee from a big publisher to publish one of his economics texts in favour of releasing it freely under a creative commons licence.
"The public-spirited professors are getting into the act by writing their own open-licensed textbooks. One of the most famous instances of this is CalTech professor R. Preston McAfee’s economics textbook, Introduction to Economic Analysis, which has been adopted at NYU and Harvard. McAfee declined to accept a $100,000 advance from a commercial publisher in order to make his textbook freely available online under a Creative Commons Attribution-NonCommercial-ShareAlike license. (This means that people are free to use and modify the book without payment or permission so long as they attribute authorship to McAfee, do not sell the textbook, and share any derivative works under the same license terms.)"