[currymj]

how much are these numbers skewed by academic monographs? these are books that are basically going to be sold only to university libraries, which might explain why they sell <500 copies.

there are many such books where no author ever expects to make money -- they have other incentives due to the way academia is organized.

[gxqoz]

My impression is that even reasonably well-selling non-fiction books typically do not sell a lot of copies. To make it onto a best-seller list you only need to sell in the tens of thousands of books.