Many of our top scientists and academics publish affordable books that are well cited and seen as seminal work. However, there are also books that go on sale for $1000 or more, written by relatively unknown authors, supposedly to disseminate knowledge and research.
If we use citation as an indicator of who has read and valued them, is there some sort of correlation between making a book financially available, and the real contribution it makes to our field (e.g. increased price = less access = less citation +/- less worth)?