You're using "sales", "commission", and "revenue" imprecisely/incorrectly. The money they collect from customers is "revenue". A portion of those revenues are

You're using "sales", "commission", and "revenue" imprecisely/incorrectly. The money they collect from customers is "revenue". A portion of those revenues are paid to the local merchant. That is the "Cost of Goods Sold". The revenue minus the COGS is the "Gross Profit". So, in your example, then they would indeed have $500M in revenue, and $250M in gross profits.