In September 2018, Logan Kane, a contributor to Seeking Alpha, stated that Robinhood's payment for order flow generated ten times the revenue as other brokers receive from market makers for the same volume. Bloomberg has analyzed Robinhood's reports to the Securities and Exchange Commission (SEC), and calculates that Robinhood generates almost half of its income from payment for order flow. Robinhood's lack of transparency on this issue is troubling. Beyond that, payment for order flow is slowly being regulated out of existence, so a brokerage that depends on generating income by selling order flow to market makers will find itself in trouble within 5 years.
https://www.investopedia.com/articles/active-trading/020515/...