You can't really compare a trials frame to a full supension dh or xc frame. I used to ride trials but have now moved to xc and freeride. The frame i have now is far more complex than any trials frame. Hydroformed tubing, linkages, bearings, support beams, rear shock etc. Trials is expensive because of relaitvely low interest in the sport (comapre it to a sport like tennis/football etc). All 'specialised' biking is the same. High specification bikes cost more to produce, this makes the initial sale price high, there aren't many people that are willing to pay hundreds of pounds for a bike. Therefore the prices remain high. Simple. Its the same for components aswell.