It's a "Law Enforcement Only" version that was not legal for us mere mortals to own for the last ten years (9/13/94 - 9/13/04) because of the AWB. Now that the AWB has sunset everyone (in non-commie states) who can legally buy a firearm can now own one.
The seller is trying to take advantage of the sudden craze to own one of these LE series rifles. Some people just have to have the latest and greatest fad, and the seller is going to profit from this. And the best way to 'cut a fat hog' is by selling in one of these auctions, where bidding frenzy often trumps good sense. This is the U.S. and capitalism is part of what makes this country great.
IMHO, these kind of prices will drop quickly once the dust from the sunset settles, all of the manufacturers get into no-ban production mode, and supply catches up with demand.
Anyway, that's my story and I'm stickin' to it
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