This is a very interesting article on why per-word rates are so low for writers for tabletop RPGS.
— Pelgrane Press Ltd (@PelgranePress) February 13, 2015
Short version: hobbyist market, consumer price expectations, high overhead, and lots of people willing to work on the cheap in exchange for having their name in a book. Don’t underestimate that last one: I got stiffed out of a flat-rate commission by one game company* – was, in fact, half-expecting it – and I still framed the first page of the adventure supplement that I had written and put it up on the wall. Because it’s different somehow when you don’t get paid even though you’re supposed to than it is when you don’t get paid because you worked for free. Psychology, or some such.
*Which will remain nameless, because, hey, they might actually still pay me at some point.