I remember, at the announcement time price dropped from 660$ to 620$, in a moment of craziness.
Then it bounced a bit but kept falling down to sub-550$. Then it recovered to 630$. After the auction ended,
it collapsed down to 500$, culminating in that 'flash crash' to 450$.
The price recovered on June 30, when the USMS announced that one bidder got all the lots. Most people concluded that his bid was above market.
The price then started a slow decline, that got worse only after one month. I don't think that this decline was related to the auction. I rather see it as a continuation of the descending trend that dominated from February to April.