Four costs recur in leveraged trading. Each can be measured, and each should be stated before any result is interpreted.
Spread
The gap between bid and ask, paid on entry. It varies by instrument, provider, account type and market conditions.
Commission
An explicit per-trade or per-volume charge on some account types, often paired with a narrower spread. Comparing accounts requires combining the two rather than looking at either alone.
Financing
Positions held past a daily cut-off are typically subject to a financing adjustment reflecting the interest differential between the two currencies plus a provider markup. The direction of this adjustment can be positive or negative depending on the position.
Slippage
The difference between the requested and executed price. It is most pronounced around scheduled events, at session opens and in thin liquidity, and it applies to protective orders as well as entries.
Why this matters for evaluating any service
Results quoted without these four items cannot be compared to what an account would have experienced. Where this publication reviews a service, cost assumptions are stated or the absence of stated assumptions is reported as a limitation.