It isn't everywhere that expensive. Mostly they cost between 200 and 250 bucks, when you have an eloxated version. The machinig of the fork ends with left- and right threads is problematic, so it's cost-intensive and aluminum itself isn't cheap. Then they are produced in 20 or 30 sets by several manufacturers and that makes them expensive. When you wait a bit longer, there will be a cheap Taiwan version, coming from Empi or Bugpack, I would bet. Then you have poorer quality but a good price and all people are crying about the quality!
Btw, my setup is self-built, costs togehter with the simple roll-cage inside totally around 80 bucks, but I machined all the screw-able ends on my own! It isn't adjustable, but machined to fit exactly!
The design is different from the normal bracings that you know, as it's fitted together with the rear ends of my roll-cage.