The reason is quite simple. They charge that much because there are enough people that will pay the price to keep them in business. That's one reason I decided to just make my own longbow. It's not a Black Widow, by any stretch of the imagination, but it's MINE. Made by me, for me, and that makes anything I shoot with it just that much more of an accomplishment.
And when I really want to go cheap, I whittle out a selfbow. Those are FREE, except for your labor.