Spread

Every time you buy at the ask and could only immediately sell back at the bid, you'd lose the spread. Tighter spreads generally mean a more liquid, more competitive market for that pair.

For example, a best bid of $59,980 and best ask of $60,020 gives a $40 spread on an asset trading around $60,000, or about 0.07% of the price — money given up on a round trip in and out, independent of any trading fee.

A common mistake is only comparing the headline maker/taker fees between exchanges while ignoring the spread. A wider spread can quietly cost more per trade than a small difference in the fee schedule.