I love the idea of eventually making the commission optional -- loyal users will continue to pay the commission and you won't have to worry about competing as much. Once there were enough loyal users, you could still support your development staff and continue to gradually build the team. What if you made the commission a sliding scale? Maybe zero to 50%, with 25% as the default? Just guessing, but I bet a lot of the people who would choose no commission over 25% commission would willingly donate 5% if given the option!