It doesn't permanently go down. But if that single seller is selling at way under the previous market price, that is what everyone is going to be paying until t

It doesn't permanently go down. But if that single seller is selling at way under the previous market price, that is what everyone is going to be paying until they run out of their supply. If this lasts long enough, it could be enough to drive entities dependent on copper production out of business or into a collapse as the price they are forced to sell at isn't profitable. Once that point is reached it doesn't matter if the price goes back up when the single seller runs out, the damage has been done.