How much revenue do academic authors make on their published books?
I co-authored a research monograph in a rather specialized area of applied mathematics.  I have received about $300 in royalties over several years.  I think this is typical.

For most authors, the important consideration is not how much money they will make, but how effectively the publisher will be able to distribute the book.  This usually means going with a well-established publisher.  I know some highly-respected authors that also shop around to find the publisher that will distribute their book for the lowest reasonable price.