there's no such thing as a free lunch
口语·书面·提醒警惕隐藏成本
例句
Be careful with that offer—there's no such thing as a free lunch.
典故来源
源自20世纪美国酒吧文化，免费午餐常伴随酒水消费，后由经济学家弗里德曼推广，指任何好处都有代价。