I would like to work for an online public auction site where visitors can surf the auctioned items free of charge; however, if they wanted to bid, then each of them has to pay a non-refundable fee, which ranges from half a dollar to two dollars, charged against running the auction and making profit. This transaction could end with making profit or incurring loss, but we are obligated to sell items according to closing bid. What is the ruling of Sharia in this regard?