Quite a lot of customers either have cash sitting in the account which they make interest on, or have margin debt which they charge for.

Interesting, thanks. For a minute I was expecting someone to say "ads"

You can Google it, but AUM at scale means .03% is a significant amount of money. There's also uninvested cash that the broker can invest in t-bills and take the spread.

Thanks for the lmgtfy :)

I bet the uninvested cash product drives some weird incentives - kpis around increasing ratio of sells to buys and increasing pain around removing cash.

Front-running your trade.

This is illegal and is absolutely the dumbest way to make money.

nice try buddy, that’s ILLEGAL