I absolutely think the only feasible business model for arbitrators is to charge a fee for each transaction. Otherwise, how can they afford to spend the time and money to investigate a dispute properly?

People are not going to want to pay for more than the cost of an item when there is a dispute, yet it could cost many more times the value of the disputed item to conduct a proper investigation and produce a fair arbitration.

Great project, by the way. Thanks for releasing it open source!