What am I missing here. A 10% commission to go to you. "This pays for the upkeep of the chatroom and doing all the work."
Your logic would never have people like Greg Susong providing a website for activity concerning a shared hobby. He sells advertising for this site, but not ANYWHERE NEAR what you sell for your site, and you want to capitalize on a successful auction sale from an individual collector?
Upkeep of the chatroom? What is that other than subscribing to one of your own advertisers offering a FREE chatroom software package to anyone with a website?
Doing what work? What is "doing all the work"? 10% ain't worth it to be listed on a weekly online auction. If work is receiving and posting emailed auction lots, sign me off. I know what real work is, and it ain't that.