This is incorrect. The benefit of order flow to the consumer is additional sources of liquidity. If a consumer submits an order to buy 500 shares of AAPL for $1

This is incorrect. The benefit of order flow to the consumer is additional sources of liquidity. If a consumer submits an order to buy 500 shares of AAPL for $100, there may only be 100 shares available on the public market at that price in which case the price of AAPL will increase from $100 to at a minimum $100.01. The way pay for flow works is that firms can execute against that order agreeing to fill any portion of it up to and including the full 500 shares. Furthermore by agreeing to pay for flow, it's a criminal offense for my firm to use that information to front run the order by buying it on the open market without first executing against the client. The allegation made by the SEC against Robinhood is that some kind of indirect front running was performed and perhaps even facilitated by Robinhood. The problem is that the SEC is pretty weak overall, and if their allegation is true then Robinhood should be punished much more severely than this $65M fine given that Robinhood and others likely profited at a minimum some $40M dollars.