Yeah, it's right on their auction site under the
link "Mandarake Auction 2002".  Link is above.
The paragraph says:

"On the day of the auction, the winner of an item 
will be determined by the one who placed the 
highest bid amount. In addition, to offset the 
high cost of running a huge auction, Mandarake 
will charge a 10% commission fee on top of the 
winning bid of each item. So after the highest 
bidder is declared, the winning bidder will need 
to pay the following... Bid price + 10% of bid 
price as commission fee + shipping fee (price 
varies depending on the weight)"

Lady Z