Mostly because they have the word 'COLT' on 'em. There's a great deal of assorted stuff around these days that you pay a premium for the brand name on it. Colt is one. So is Browning, Winchester, Weatherby and a bunch more.
Applies to car parts too. The exact same car horn goes in a Chev that goes in a Cadillac, but if you say you want one for a Caddy, it'll cost more. No dinner or sweet nothings whispered in your ear either.