Many of the comments talks about the price of books like those required for college courses, and the article don't really make a big deal of this, but the statistic it uses does specifically say "recreational books".

If your first language is English I assume that this is less of an issue, but the problem is that not enough books are being translated anymore. Translation is expensive, and no, AI cannot do this very well yet. So yes, books are pretty cheap, their are also all either shitty cookbooks, biographies or crime novels. If you want to learn something new, you better learn to read English at a fairly high level.

My take is that yes, books are fairly cheap, but part of that is because the cost is kept down by limiting the selection to exclude a large variety of books that are no longer economical to publish. Leaving us with only the mass market books that can be printed in volumes and sold in supermarkets.

Go buy used books, they are frequently only a few Euros because no one wants them. There's a insane back catalogue of well written books in your language to be found used, and the printing quality is often very good, and if not you paid maybe €2.