There would not be brokerage fees for ever trade. If I put in a trade for 100k shares and 20k is filled and 10 mins later 20k is filled; as long as the same day, I will only have one fee. Next day would be another fee. Also who knows who they are, people with more money or a certain amount of trades trailing a 3 month period can result in even cheaper broker fees or potentially none in some cases.