so I list loads of something at £250.00 (say 5000 1p coins at £250 each)
You all buy one each from me.... with 20% of, you pay £200. I get £250 from paypal minus fees.
My value fee is 10%, so I pay £25.00 to ebay. I split the £25.00 minus the paypal transaction fee (maybe £5-£10) leaving £15 profit...
Split £15 50%/50% with each of you 5000 members and I get £37,500 profit.