Those have to be very special sang.
There were also just under a pound and a half sold for around $600 recently on eBay.
Long neck, clean,fine root hair, good growth rings, well dried etc...you don't want to buy sang with too much dirt at that kind of price... Probably the buyer is a collector. He is willing and able to reward a careful digger.
Most roots in the $400-800/lb range are regular roots, with some broken/damaged roots and which still require cleaning before they can be eaten.