compare prices for mountain bikes...
My insurance company recently bought me a very high end mountain bike - an Ibis Mojo SL WTF. I had not been in a bike store for a long time, and I was flabbergasted at the price differences between mountain and road equipment.
As far as I can tell, the Mojo SL is one of the most advanced carbon fiber frames ever made, yet it costs less than $2500. "Me too" full suspension carbon mountain frames from Trek, Specialized, Santa Cruz, and Giant, for comparison, are all under $3000, and most are between $2000 and $2500. A super high end mountain bike fork such as a DT Swiss will run ~$1500, and the more common Fox, Rock Shox, and Manitou top end offerings for trail bikes are $800-$1000. So you'd be hard pressed to spend more than $5K for a frame / fork, and many arguments could be made that you could get "the absolute best" F&F for right around $3000.
By comparison, as noted by many other posters to this thread, road bike F&F prices can be $5000 and up.
When you look at the grouppo price differences, whether your preference is SRAM Red or Shimano XTR, the entire set is around $2000. Again, about half the price of the road bike equivalent. If you read your average mountain bike magazine, rarely do they test complete bikes costing more than $6000. They exist, but they're not common, unlike their road going brethren.
As a consumer of both, I think mountain bike technology is more advanced than road bike technology. Forks have complicated dampers, derailleurs are subjected to greater forces, etc. Testing reflects this, as well. For instance, the Ibis frame requires a 1300lb force to crack the headtube, and the downtube can be attacked by people swinging baseball bats and emerge unscathed.
My conclusion is that the price differences reflect the different markets, NOT the differences in technology. Road bikes are being marketed to baby boomers with deep pockets who want to look and feel vital. They can get into the sport with a $10,000 splash, and get into great shape, with minimal technical ability. If you could ride a bike as a kid, you can learn to clip into pedals and go for a ten mile road ride to start with some dedication, be doing centuries in 6-9 months.
Mountain biking is a different story. Unless you are incredibly gifted, it requires lots of time and humiliation spent on mastering the technical aspects (read - crashing and loooking like an idiot in front of your friends)before you can even begin to appreciate a bike like a Trek Fuel or Santa Cruz Blur. There is very little instant gratification, and after a day of riding through the mud, even a $7500 Ibis looks like crap.
Since high end mountain bikes can only be sold to "dedicated" cyclists, the prices better reflect the development and production costs. In contrast, high end road bikes can be sold and appreciated by anyone with enough financial wherewithal, so all the more power to that larger population.