Later: to be clear, my subtext is that Robinhood customers aren't actually paying anything and are sort of getting a free lunch here. The money Robinhood pockets from your trades isn't available to you in any form, at least until someone starts the brokerage that pays you to trade.
1. RH user wants to buy 1000 shares of XYZ. Offer price is $10.00
2. RH forwards the full order to their execution venue partner. They get paid (assuming SeekingAlpha story is true) $260/$1mm traded, or $2.60.
3. Executor takes the order and immediately sends 900 shares to the market, lifting the offers. Now best offer is $10.10
4. Executor facilitates the tail of the order, 100 shares, at $10.10. So they are short -100 shares here - or they can give a de minimis price improvement (like 10.0985) to meet their contractual obligations.
5. Temporary market impact attenuates and offer mean reverts to $10.05
6. Executor still has risk on their books - but their paper mark-to-market profit is $5.00.
7. Risk can be mitigated by waiting for crossing order or waiting for more favorable offers to close out the short.
So roughly speaking they paid $2.60 to get the order, but made $5 on it...
You could have saved the hypothetical $2.40 had you traded differently, albeit slower, and caused less market impact with your order. Of course, trading slower comes with its own slippage risk or opportunity cost that the market moves out of your favor. But it could also move in your favor... However, if you let a greedy HFT use your order to impact the market - it will always be out of your favor.
For a small retail guy, you are powerless unless there is a RobinHood 2.0 that decides to offer comm-free trades + does not sell your orders + makes money doing something else ... stock loan maybe?
EDIT: Also the HFTs hate limit orders because it reduces the amount they can internalize. They also generally have a contractual obligation to always execute your order. So you can always use a limit at or inside the offer if youre buying, and potentially save on that cost.
This is why I asked for specificity. Yes, we agree, internalizers pay for order flow because they can make money on it. The question is: can you make that money on your own order flow, or is the allocation of orders to internalizers Pareto-optimal?
It is possible to build one, but it would look so different from existing markets that it would be an uphill battle to get people to adopt it.
The flow I explained in one way these guys make money. It's certainly exaggerated. At the one place I worked we ran a $0.5bn book of this stuff. You don't always get chances to get out. So risk management is key. Your book turns over every few days.
And it's not like a lot of internalizers are going around with prospectuses saying "we're gonna purposefully move markets to give your customers worse prices", so the SEC isn't going to have much trouble fining them if they decide to (assuming this is actually happening all the time).
Yeah I don't really care about the semantics here, it is commissionless. My strategies aren't materially affected by some broker-level BS, I am satisfied with the fills I get on Robinhood vs what I can see on the order books using other tools.