Poor Guy Havaard payed a pretty price to be part of the Demigod GST when they won last year. Tons more than 15 USD, I will tell you that. They couldn't scam him, not for the amount he payed.
But in any event like this, I believe it is against Graal's policy to allow for transfer of real world currency for in-game items between players. So from the start, it should be brought to GP attention. Although, anyone who does end up paying currency under the radar for something like this should not be cheated out of his or her money, but I cannot support these types of transactions. I don't want to say these people get what they deserve, but they should really be more careful with their money.