To expand on this: if the book can provide value above and beyond its selling price, it is a worthwhile purchase.
Your examples of "how to price" are all focused on what the author wants (or what he can get away with). The way to justify a higher price is to focus on what the READER wants, and the value they will get out of the book.
An ebook about learning React, for instance, might be worth $39 because it will save the reader HOURS of reading through random blog posts. How much is their time worth? (source: I wrote and sell an ebook about this. People actually buy it :)
Your examples of "how to price" are all focused on what the author wants (or what he can get away with). The way to justify a higher price is to focus on what the READER wants, and the value they will get out of the book.
An ebook about learning React, for instance, might be worth $39 because it will save the reader HOURS of reading through random blog posts. How much is their time worth? (source: I wrote and sell an ebook about this. People actually buy it :)