I think this has more to do with your target audience. The books in question are aimed at an audience which overall has a really good purchasing power. To many

I think this has more to do with your target audience. The books in question are aimed at an audience which overall has a really good purchasing power. To many people 15 euros is an expensive book but looking at my tech books shelf, and seeing an average price of around 50 euros(many of which I would have paid double without a single doubt of hesitation), you quickly see a huge gap between the different audiences. Good developers and tech people certainly appreciate the complexity of tech books and are well aware that they are often guides to prototypes, as opposed to full, production solutions. Hence the reason why many are more than happy to support open source projects from our own pockets. Take "The Rust Programming Language" book for instance - it's completely free online but I was more than happy to purchase the paper version in order to support the authors, the same way I donate to the Linux foundation, the PSF foundation and so on. And sure enough, I appreciate someone's hard work here and I'd happily buy their books should I see them useful to me. I can't recall which artist it was (I recall it being Jan Garbarek but don't quote me on this) who gave away an album online where you could get it for free or any amount you like. I recall several sales in the 5-digits which is a clear message. But much like textbooks, such music has a very particular audience and such... Let's call them "stunts" wouldn't be successful for most products and would backfire terribly.