I guess the bottom line is performance. While it may not come cheap, it IS there. The guy that makes the uppers shoots long-range competions with the upper pictured above, and wins, and that's with his trigger as well. He re-works the trigger to be much more than a milspec trigger, and they break at 3 pounds nicely.
I don't feel like $1900 is out of line for a truly custom rifle when Bushmaster sells models like the Predator or Varminter for not much less than that.
Then you get to their custom shop....
http://www.bushmaster.com/bcs/BCWPMR18.aspMay not be for everyone's tastes though.