cost someone an arm and leg: 花大价钱， 花了一大笔钱（花一只手臂，一条腿的价格， 跟“卖肾”差不多了）

【例句】
It costs me an arm and a leg to get this house.
买这套房子花了我一笔钱。

He bought his girlfriend a necklace, but it really costed him an arm and a leg.
他给女友买了一根项链， 但真的花了他一大笔钱。