[backzerman]

> The customers are the businesses on the other end, in Robinhood's case the market makers who are paying for the right to front-run trades.

Front-running is super illegal. You're referring to payment for order flow (PFOF), in which a sell-side party like Citadel pays Robinhood for the right to route your order to the exchange. But there's a catch: Citadel is allowed to take the other side of your trade without routing it to an exchange, but it legally has to match the exchange price or cut you a discount. If Citadel can't do either, your order MUST be routed to an exchange.

PFOF makes up a somewhat negligible source of revenue for no-fee/discount brokerages. The bulk of revenue comes from a much more mundane source: interest rate spreads. Earn X% interest on customer cash deposits while providing customers less than X% interest on their deposits.

If your order isn't making its way to an exchange, PFOF isn't your problem, and you shouldn't be day trading. Your real problem is that the professionals think you over-bid/under-asked to such an extent that they're willing to cut you a deal just to take the other side of your trade. Unless you're a professional options trader, betting against professional market makers will cost you a lot more money than the imaginary transaction costs would have.

(This is just a summary of an old HN favorite: https://www.kalzumeus.com/2019/6/26/how-brokerages-make-mone...)