I really don't have a problem with the "overpricing." Cheeze. I had this explained to me some time ago. I hate inflation in general. Although I think World's Largest Dungeon is cheesy (where am I going to find the room to stuff that!), I really think that the "overpricing" is actually fair for the producer and the consumer.
RPGs are always luxury items. Unlike the science books I buy to support my learning habit (I habitually learn, every second that I'm awake), which I consider important, RPGs are lux items.
Strangely enough, the Science Books help me DM. I bought a book on the Dinosaurs of Utah, and a book on Desert Ecology. Strangely enough, they help more than hinder.

I also have books on Roman Britain (which I will use) and Greek Society (which I use), and a Chinese History book (which I find very, very useful). Next on my buy list (between a recovered gymnophobe girlfriend [I need to find one!]):
* A travel book to Hong Kong.
* A book about Stonehenge.
* A book on Ancient Egypt.
* A book on Astronomy.
* The (apocryphal) Book of Enoch
* A book on medieval and Roman Cuisine.
* A U.S. Passport.
* Tickets to Bombay India.
Okay, I go too far on those last two. So, really, RPG books are not overpriced. And steadily, I get more use out of actual books on Ecology than I do RPG books written for that purpose.