Academics are being hoodwinked into writing books nobody can buy
Academics spend years writing books nobody will buy.  That's practically the definition of academic writing.  They go into incredible amount of depths for a very, very niche audience: other academics interested in, e.g., the experience of women in Japanese detective novels of the 19th century.  (n.b. Actually a book, assuming I am remembering all the details correctly.  An advisor spent years on it.)This is exactly the result the market should hope for: a profitable method which gets academics to write down very-incredibly-niche ideas and then put copies of them exactly where someone would expect to find very-incredibly-niche ideas.  The alternative to these $150 books is not $7.50 books.  It is "no book."  They do not meaningfully trade off with equally-in-depth blog posts, because academics are not scored on, and hence do not as a matter of practice actually sit down and write, book-length blog posts.