1. Something will cost a large amount of money, especially compared to a cheaper or simpler option. You can opt to rent a larger van instead of the sedan, but it will cost you. A: "Jane and Joe want to upgrade their tickets to first class." B: "There's still time to do it, but that'll cost them. Are they sure it's worth it?" A: "Will you promose not to tell Mom?" B: "It'll cost you."

2. Something will have a negative impact on one's performance or chance of success. A: "Uh oh, the quarterback just fumbled the ball on his own 20 yard line!" B: "Ouch, that'll cost them big time. They really can't afford to give up any more points this late in the game." You can try to fluff up your résumé a bit when you apply for the job, but it'll cost you if your interviewers find out.