I watch the auctions and keep a record of the 'buy it now' sales. For example, one seller has sold 199+ ounces of silver for $50+. Interesting to watch.
The same 1 ounce minted bar.
Perth Mint price $28.77
Ebay purchased prices $52.95
84%+ Increase
The same can be said for gold - 1g for example is 48%+ more and selling like hot cakes.