都表示花费时间、金钱.cost是花费,一般用于某某东西花了多少钱.e.gThepencostme5yuan.固定短语spend...on/spend...indoingsth.e.gIspend1houronhomework./Ispend1hour(in)doinghomework.pay是付钱,短语payfor译为为...付钱.e.gIpay25$forthisbag.