How Trading Costs Change With Your Style

The short answer

Per-trade costs scale with how often you trade. Time-based costs scale with how long you hold. For a high-frequency approach the spread dominates and financing barely registers; for a position held for months, overnight financing can exceed every entry and exit cost combined.

Every cost on this site applies to every trader. What differs is how often you meet each one, and that single fact reorders the entire list depending on how you trade.

This is why "which broker is cheapest" has no answer in general, and a clear answer once you say how you intend to trade.

Two kinds of cost

Sort the ledger by what each cost scales with and it splits cleanly in two.

Per-trade costs are paid each time you open and close: the spread, commission, slippage. They scale with frequency. Doubling your number of trades doubles them, regardless of how long each lasted.

Time-based costs are paid for as long as the position exists: overnight financing above all. They scale with duration. Doubling your holding period doubles them, regardless of how many trades you placed.

Almost no approach is equally exposed to both. The two scale on different axes, and most strategies sit heavily on one.

What dominates, by approach

High frequency — many trades, held briefly. The spread is the dominant term, by a distance. Commission is second. Financing is close to zero because positions rarely survive the cut-off. Slippage matters disproportionately, because the edge being pursued is often smaller than the cost of a poor fill.

For this style a small difference in spread is not a detail; it is the difference between a workable approach and an unworkable one. Everything else is secondary.

Intraday — several trades a day, flat by the close. Spread and commission still dominate, financing still absent. Timing matters more than for anyone else, because a trader active through session edges and releases meets the widest spreads of the day as a matter of routine rather than accident.

Multi-day to multi-week. The balance shifts. Per-trade costs are amortised across a longer and larger move. Financing starts to register and compounds quietly. The trader who is most often surprised by their total cost is here, because they are still thinking in terms of spread while paying mostly for time.

Months. Financing is usually the largest single cost, often by a wide margin over every entry and exit combined. The spread matters once, at each end, against a position that existed for a hundred nights. A tight spread is close to irrelevant here, and a financing rate is close to everything.

The arithmetic that decides it

The useful calculation is not the cost of one trade. It is the cost of a year of behaving the way you actually behave.

For a per-trade cost: cost per round turn × trades per year. For a time cost: nightly rate × nights held × position size, summed over positions.

Run both. One will be several times the other, and that is your real cost base. Optimising the smaller one is effort spent on the wrong term.

We are not supplying figures. Spreads, commissions and financing rates vary by broker, instrument, account and hour, and a worked example built on invented inputs would produce a confident answer to a question nobody asked. Use your own broker's published numbers and your own trade count.

Choosing the account to match

Once you know which term dominates, the account choice follows.

A raw-spread account with a commission usually favours high frequency, because the spread is the thing being minimised and the fee is predictable.

A wider-spread, zero-commission account can favour low frequency and large size, where a per-lot fee would be the larger number.

For long holds, neither matters as much as the financing rate and whether the base currency avoids a conversion on every position.

None of this is a recommendation of any firm. It is a statement about which number to compare, which is the part most comparisons skip.

A note on what "best execution" does not settle

Firms operating under MiFID II must take all sufficient steps to obtain the best possible result for clients, and for retail clients that result is assessed on total consideration: price together with the costs associated with execution.

That is an obligation about how a firm executes your orders. It is not an assurance that the firm's fee structure suits your strategy, and no regulation can be, because the suitability depends entirely on behaviour the firm does not control — how often you trade and how long you hold.

That part remains yours. It is also, on this ledger, one of the few things that genuinely is.

Where this sits

This page reorders each component in turn according to how you actually trade.