Every buy and every sell costs money. The fee is charged by the broker or exchange, as a fixed amount, a percentage or both. The is the gap between the buying and the selling price. happens when the fill differs from the planned price. Because costs arise when buying and when selling, every trade counts twice.
Our cost model
Our tests calculate per side, i.e. when buying and when selling: stocks 0.10% fee plus 0.05% slippage, together 0.15%; crypto 0.10% plus 0.10%, together 0.20%. For buying and selling together that is about 0.30% and 0.40%. The tests do not count a spread separately; in effect it is included in the slippage.
Do the math
Model: stake €5,000, costs 0.20% per side. Buying €10, selling about €10, together €20. With 50 trades a year that is €1,000 – with €10,000 capital, 10% that the trades first have to earn.
Fixed fees and small trades
A fixed fee hits small trades hard: €5 per order is 1% per side with a €500 stake, only 0.1% with €5,000. If you trade small amounts often, you need bigger price moves just to cover the costs.