Round Trip Transaction Costs

See: Alligator Spread.

You bought shares of whatever.com for $27, then sold them at the end of the day for $27, after watching them kiss $28 (with no tongue), only to slide back to $27 even at the end of the day. It was a round trip on the shares' price, from $27 to $28, and back.

So you broke even, right? No, not at all. You paid commission when you bought, and then commission when you sold, so you had something like a dime or so in transaction costs and actually netted $26.90 at the end, losing that dime for your troubles.