I worked as editor for O'Reilly and am an author for O'Reilly, and there's no page count juju in our royalty payments. You get paid 10% of what we get for books that sell. End of story (for print, things get weirder in ebooks but not so weird that pages enter into the picture).

The only thing that's important about page count is that there be enough pages that the book's title is visible on shelves and not so many that you need to reinforce those shelves.

This minimum page count, by the way, is why so many business books suck: they have an idea and examples that they could get across in 10-20 pages but have to stretch it to 300 generously-whitespaced repetitive pages in order to have a physical object on shelves to sell. For this reason alone, we should hail Kindle and other ebook platforms that let you make money from 20 pages. If I never again have to read the business equivalent of an ASCII table, I'll be a happy man.