I would offer that the vast majority of the sets have not yet been delivered by the Mint to those that ordered them. Give it a little time, I bet they will start to appear in the marketplace.
Also, those with confirmed orders may be hesitant to offer pre-sales online due to the recent volatility of silver's spot price and/or not yet knowing how many of the sets will ultimately be sold. Few sellers want to leave money on the table!
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