A commission based on a percentage of the winning bidder's price refers to a fee that is added to the final sale price of an item. Here's how it works:

1. Winning Bid: When an auction concludes, the highest bid submitted by a bidder becomes the winning bid. For example, if a bidder wins an auction with a bid of $100.

2. Commission Percentage: The auction house or seller may charge a commission fee, which is a percentage of the winning bid. For instance, if the commission rate is 10%, this means the bidder will pay an additional fee calculated as 10% of the winning bid.

3. Total Amount Paid: To determine the total amount the winning bidder must pay, you would calculate the commission based on the winning bid and add it to the winning bid itself. Using the previous example:

   • Winning Bid: $100
   • Commission (10% of $100): $10
   • Total Amount Paid by Bidder: $100 (winning bid) + $10 (commission) = $110

In summary, the commission is an additional cost that the winning bidder must pay on top of the sale price of the item, calculated as a percentage of that price.