You can have a strategy that wins more than it loses and still bleed an account to death. The culprit isn’t your entries — it’s the toll booth you pass through on every single trade, twice, that never shows up in your backtest.
Spread and commission are a per-trade tax, and until you price it in, you don’t actually know whether your edge is real.
Spread + Commission as a Per-Trade Cost
Every forex trade pays two possible costs before it can profit:
- Spread — the gap between the bid and ask. You buy at the ask and sell at the bid, so you start every trade already down by the spread. It’s baked into the price, which is exactly why it’s easy to ignore.
- Commission — a flat fee per lot per side, charged on some account types. Unlike spread, it’s an explicit line item, so at least you can see it.
Together these form your cost per round trip: what it costs to open and close one position, before the market has done anything. A “0.2 pip spread plus $3.50 per lot per side” account and a “1.2 pip spread, zero commission” account can cost roughly the same all-in — the total is what matters, not which bucket it sits in.
The trap is that costs are invisible in the moment. A losing trade feels like the market’s fault; you rarely notice that the spread and commission made the hole a little deeper on the way in.
Raw vs Standard Accounts on Prop Platforms
Prop-backed brokers typically offer two flavors of pricing, and the right one depends entirely on how you trade:
| Raw / ECN account | Standard account | |
|---|---|---|
| Spread | Very tight, near-interbank | Wider, marked up |
| Commission | Explicit fee per lot per side | None (built into the spread) |
| Best for | Frequent traders, scalpers | Swing traders, low volume |
| Cost is… | Visible and itemized | Hidden inside the price |
Neither is cheaper by default — they’re two ways of charging for the same thing. A raw account wins for high-frequency styles because the tight spread saves more than the commission costs. A standard account can be simpler for low-frequency swing trading where a slightly wider spread on a handful of trades barely registers. Do the round-trip math for your trade count before assuming “raw = cheaper.”
Whatever your firm offers, confirm the exact spread and commission schedule for the account type they issue — it varies by program and directly changes your break-even.
How Costs Quietly Turn Positive Expectancy Negative
Here’s the mechanism that catches traders out. Expectancy is your average profit per trade across wins and losses. Costs subtract from every trade, win or lose — so they pull your average expectancy down by roughly the full round-trip cost, every time.
If your raw edge is, say, a few dollars of expectancy per trade and your round-trip cost is a comparable few dollars, your real expectancy is near zero — or negative. The backtest that looked like a money machine was measuring a version of your strategy that never paid the toll.
- A strategy with large average wins and few trades barely notices the tax.
- A strategy with small edges and many trades can be entirely consumed by it.
The uncomfortable truth: cost doesn’t just shave your profit, it can invert your sign. Positive on paper, negative in reality. The only way to know which side of zero you’re on is to measure expectancy with costs included — the raw number is a fantasy.
Costs Hit Scalpers Hardest — The Round-Trip Math
Scalping magnifies the tax because the cost is roughly constant per trade while the target is small. The relationship is brutal and simple: cost as a share of your target = round-trip cost ÷ profit target.
Chase a 5-pip target while paying a 1.5-pip all-in cost and you’re handing over close to a third of every winner before you begin — and you still have to be right often enough to cover the losers on top. Aim for a 50-pip swing with the same cost and the toll is a rounding error.
This is why the same account, the same broker, and the same spread can be perfectly fine for a swing trader and quietly fatal for a scalper. If your style is high-frequency, your first job isn’t finding better entries — it’s minimizing round-trip cost, because that’s the biggest single input to whether your edge survives contact with reality.
Measuring Cost-Adjusted Expectancy From Real Trades
The only honest measure of an edge is expectancy computed from your actual filled trades, net of what you actually paid — not from mid-price backtests that never crossed a spread. To get there you need every trade’s real entry, exit, and cost captured, which is exactly what a dedicated forex journal buys you over a spreadsheet or a tool that only logs price. Compared to price-only journals like Edgewonk, the value is having costs folded in automatically rather than reconstructed by hand.
Concretely:
- Pull your net PnL per trade — after spread and commission — not the gross move.
- Feed the wins and losses into an expectancy calculator to see your true per-trade average.
- If cost-adjusted expectancy is thin or negative, you have two levers: raise your average reward-to-risk (so cost is a smaller share of each winner) or cut trade frequency (so you pay the tax less often). The full picture is worth understanding — trading expectancy walks through why a positive net number is the only one that matters.
Shibiki does this the tedious way so you don’t have to: it auto-journals every fill straight from the platform — the MT5 integration reads real entries, exits and costs — and computes your edge health as a Wilson confidence interval on your win rate, so you can tell a genuinely profitable system from one that only looked profitable before the toll booth.
Related: Expectancy calculator · Trading expectancy, explained · MT5 integration