The cost nobody puts in the backtest

Gold pays no income, so a long gold CFD is a financed position. Your broker charges you for that financing every night you hold it. Most traders never compute this number, and it is frequently larger than they expect.

Here is the scale. At $4,300 an ounce, one lot is $430,000 of notional. Financing at roughly 5% a year is about $59 a night, or roughly $1,770 over a month. On a 0.10 lot that is still $6 a night — small in absolute terms, but very large relative to a $50 risk budget.

The three costs that eat a swing trade

Financing (swap). Charged nightly on the notional, usually at a reference rate plus an admin fee. Longs pay; shorts may receive less than the reference rate, or pay too, depending on the broker. Triple on Wednesday for most brokers, to cover the weekend.
Spread. Gold spreads are tight in New York and noticeably wider in Asia and around data. Paying three times the normal spread because you entered at the wrong time is a real cost.
Margin. Not a cost, but it determines what else you can do. Gold notional is large, so a position that risks 1% can still consume a big share of your free margin — and that constrains you exactly when opportunities appear.

Break-even is a real number

Before entering any gold position with a multi-day horizon, compute the break-even move: the price change you need just to cover round-trip spread plus carry. If your target is inside that number, the trade has no edge regardless of how good the setup looks.

How to check this yourself

Before you place a swing trade, write four numbers on paper: your account size, the percentage you are willing to risk, your stop distance in dollars, and your expected holding period in days. Then check your broker's overnight swap rate for that position size and multiply it out. Most traders discover at this step that the carry costs more than the move they were targeting.