Actually he not insider.

The trick is to have some friends whose business have merchant accounts with low MDR(i am sure you know some if you are a businessman like this guy). Then swipe your participating card to these friend's terminals to match the contest rule. There is "investment cost" for this trick though, as he will need to rugi the transaction fee to the banks if he fails to win. It could be some kind of JV(revenue share if win prize) between him and the friends who lends him their merchant account.