Example 1: Same setup, two instruments
Two traders take the same breakout setup on the same day. One trades a liquid index future with a tiny spread and deep order book; the breakout fills at the expected price and the cost of entering is negligible. The other trades a thinly-traded instrument with a wide spread; the same breakout fills several ticks worse, the spread eats a chunk of the move, and an exit in the fast part of the move slips further. The analysis was identical; the instrument decided how much of the move each trader actually kept.
