Considering so few were printed, the only reason they are available in large numbers and at reasonable prices is due to the high survival rate. High denominations don't circulate as much as lower ones. In addition, this was the last Legal Tender series and some folks likely held onto them knowing they might carry some kind of premium years down the road.
Cool, I'm trying to upload a picture of it. It's in nice shape other than the defined center fold. First time on this site but I'll be posting more since I strap and coin roll hunt in large quantity. Just scooped some be straps today with some nice seriel #'s