I want to point out that the fee structure in Challenge Matches is rather unfair. I was reviewing my account today and realized that the fee is charged to both a winner and a looser (I thought it was only to a looser at first). In essence, one is risking 100 credits to only win 80. This is a very large spread, which amounts essentially to a 25% fee on every match(100/80 is 1.25). In reality you are playing for 90 credits and then are charged 10 additional credits whether you win or loose.
This fee structure is very unfavorable to playing challenge matches which, I believe, is a great part of this site. I would propose to use the same fee structure that is used in most betting circles, which is that the winner is not charged and the looser is charged a 10% fee. In essence, you would risk 110 credits to win 100. This would make it a much more fair experience and, I believe, would increase dramatically the total number of Challenge matches played.