Why trading frequency matters
A fixed fee is proportionally larger for a small trade than a large trade. Changing how often a trade is placed changes the yearly number of fees. There are other factors; including time out of the market and product or platform conditions; that this simple arithmetic does not model.
What is not included
This calculation does not include changes in market value, bid-ask spreads, fund fees, currency costs or tax. It assumes a constant per-trade cost and that monthly amounts can accumulate between trades.