You would be right, if the goods sold were purchased by the retailer and then resold. In that situation, you would have revenue and CoGS. However, often retails

You would be right, if the goods sold were purchased by the retailer and then resold. In that situation, you would have revenue and CoGS. However, often retails do not own the goods they sell. In that situation the price paid for the widget is not the revenue of the retailer. It counts as the GMV, and the revenue is the portion that goes to the retailer.