More likely their money comes from impatient traders who pay the spread to them. They compete for that spread with other firms like them.
The impatient spread-crosser is happy to be filled and move on to doing whatever it is they do for a living rather than playing trader. You can send a marketable order for a liquid ETF to any exchange in the US and at worst you'll be a tick away from the NAV. You don't have to compute the basket value. You don't have to watch the order books for 500 stocks on 10 exchanges. You don't have to monitor the futures markets or trade in them. One click and someone else does all that work for a penny. How is that not valuable?
What specifically did you find unethical about them?
The impatient spread-crosser is happy to be filled and move on to doing whatever it is they do for a living rather than playing trader. You can send a marketable order for a liquid ETF to any exchange in the US and at worst you'll be a tick away from the NAV. You don't have to compute the basket value. You don't have to watch the order books for 500 stocks on 10 exchanges. You don't have to monitor the futures markets or trade in them. One click and someone else does all that work for a penny. How is that not valuable?
What specifically did you find unethical about them?