> They give their users inferior prices and then collect on the arbitrage.

That’s false. They’re legally required to get the national best bid or ask just like any other broker. Routing trade flow doesn’t change that, it just gives the recipient the ability to match or beat those prices. If there was a better price elsewhere they’re mandated by law to attain that price. If they’re not doing that the SEC would be en route.

Literally settled with SEC a month ago for exactly that. https://www.sec.gov/news/press-release/2020-321

Ha! That’s incredible. I can’t believe anyone would keep their account there after something so brazen comes to light.

If a Robinhood trade is being matched with a better price after it routes then Robinhood didn't offer them the best price. It's how Robinhood makes money. This is the heart of their deal with Citadel Securities. And, yes, the SEC is indeed on their case about this. It's how we know about it.

"How Robinhood makes money on customer trades despite making it free" https://www-cnbc-com.cdn.ampproject.org/v/s/www.cnbc.com/amp...

Robinhood basically sells right of first refusal on "dumb flow," which is valuable. The buyer can route it to someone else if they don't like it, but they get to decide before them. Also they get information from retail investor orders before the rest of the market gets to see them and can adjust pricing on other offers in related symbols before others get to react.