Spread and slippage rarely show up as a single dramatic loss, which is exactly why traders underestimate them. They're a small tax on every trade that quietly compounds over hundreds of executions.
1. Spread's outsized impact on frequent trading
A trader targeting 20-30 points per trade who pays a 3-point spread is giving up 10-15% of the potential gain before the trade even starts working. A swing trader targeting 200+ points barely notices the same spread. The faster and more frequent the strategy, the more spread cost matters relative to the profit target.
2. When slippage gets worse
Slippage, the gap between the price you expected and the price you actually got filled at, widens during news releases, session opens, and any period of thin liquidity, the same conditions that widen spreads. A market order placed right at a major release can fill meaningfully worse than the quoted price at the moment you clicked.
3. Measuring the real cost
Rather than comparing brokers on advertised spread alone, track your own actual fill quality over a month, expected entry versus actual entry, expected exit versus actual exit, and sum the difference. That real number, not the marketing figure, is what's actually being subtracted from your results.