Just got this email from the mint they must be paying a premium above spot for the real deal.
"LIMITED TIME OFFER Order before 4th January 2011 to guarantee current silver prices!
The price of silver has increased dramatically in the last few months. From the 4th of January 2011 The Perth Mint will be increasing the price of silver coins. So, if you are thinking about buying a silver coin order now to beat the price rise. Click the BUY NOW button to view our extensive range"