Fifteen years ago, I wrote RPGs for 3 cents a word. In these more modern times, though, the pay rate is... wait, it's still 3 cents a word. Come to think of it, the pay hasn't changed much from the golden age of pulps and early sci-fi. The pay is the same as from the 1950s? What's wrong with this picture?
One argument is 'that is all the market will bear'. Okay, but in that same timeframe, other forms of writing (particularly journalism and non-fiction) moved on to dollar-a-word. Sure, we're in a dip for that sort of writing too, with rates often dropped to half that. But a pair o' quarters per word is still a damn site better than RPGing's 3-cents-per.
The part that makes this discussion so painful is that the quality of writing can really make or break what is fundamentally a book project. This is one place where markets really don't seem to be able to adapt as the low rates often lead to weak product. Maybe this is just a consequence of niche markets?