At last check a Barret M-82 .50BMG rifle was selling for about 3 grand.
A note on the .475 Linebaugh, according to an article I read about a year ago in a reputable gun magazine, when this round first started seeing use in beg game hunting in Africa it was found to be able to put an African bull elephant down, permanently, with a single head shot. I know you might be thinking "Of course, they shot the elephant in the head!"
But an elephant's skull is if I remember correctly about 6" thick. Supossedly after one such shot the hunter wanted to check where his bullet ended up and found it not in the skull but in about the fourth vertebrae. That is a lot of bone to punch through!!