I look at this a slightly different way. For me, the question is Are fantasy novels pricing themselves out of the market?
Now, this may be a legacy of living in Australia, but the newest Stephen Donaldson hardcover (The Runes of the Earth) cost me more than Complete Adventurer.
Checking online, the undiscounted price is $26.95 (US). Complete Adventurer is $29.95 (US). Due to the different places I bought them at, CV actually cost me less money than RotE.
The price of novels has significantly increased in the past few years. Chainfire by Terry Goodkind, is $29.95 (US) in hardcover. Mass-market paperback is cheaper (around $8 US?), but that's still a significant sum, especially comparing it to previous years.
So, when I compare the price of books in general with those of RPG books, and how both have been increasing of late, I don't think it's exactly a problem of RPG books alone being "too expensive" - whatever that is.
Cheers!