In return for access to order data, Robinhood has sold about $69 million of information in 2018 to give firms like Citadel Securities more information than is available to retail investors — specifically, first access to trade patterns a few milliseconds before they get filled. This was said to be about more than 40% of Robinhood’s total revenue in 2018 by three anonymous sources in Bloomberg, something that looks to have invited a SEC probe.

This allows for automated trades to have an edge with faster data than the rest of the market. The old adage holds true here — if you’re not paying for the product (after all, Robinhood built its userbase on the premise of commission-free trades) then you probably are the product.