Stuff is "worth" whatever people are willing to pay for it. (And the seller is included in that, his lowest sell price is what he's willing to pay to keep it)
If no one is willing to buy it at this price, then it's worth that much to the seller to keep it himself. So it is worth that much to him. If someone is willing to buy it for that much, then it is worth that much to them to buy it.
