[dragonwriter]

A more accurate statement would be that you are the supplier of several key inputs (both data and ad viewership), that are used in creating the product that they sell to customers paying money, and that, as a supplier, you are paid with the products you consume (e.g., gmail, etc.)

Another (equivalent) accurate way is that you are, in fact, a paying customer for the product you are consuming, but a customer that pays in-kind with things that they use to create another product that they sell to people who pay with money.