口诀：只有人才会PS(photoshop),所以主语是人的两种花费是 pay 和 spend。
1.人 pay 金钱 for sth. 付钱买... pay-paid-paid
我花200美元买了一件裙子。
I pay 200 dollars for a dress.
2.人 spend 时间/金钱 on sth. 或 人 spend 时间/金钱 （in）doing sth. （in 可以省略） spend-spent-spent
a. 我花2个小时做作业。
I spend 2 hours on my homework.
I spend 2 hours (in) doing my homework.
b.我花200美元买了一件裙子。
I spend 200 dollars on a dress.
I spend 200 dollars (in) buying a dress.
3.物 cost sb. 金钱 某物花费（某人）多少钱 cost-cost-cost
这件裙子花费了我200美元。
This dress costs me 200 dollars.
4.It takes sb. 时间 to do sth.做某事花费某人多少时间 (It 作为形式主语) take-took-taken
我花2个小时做作业。
It takes me 2 hours to do my homework.
小试牛刀：
1.---How much does your new bike________?
---I ________ 300 yuan ________ it.
A. pay; spend...on B. cost, buy...for C. spend; paid...on D. cost;paid...for
解析： D
How much does your new bike___?这句话的your new bike是物，所以我们只能选择cost.
下一句 人作主语，人 pay 金钱 for sth. 付钱买..., paid 是pay的过去时。
2.It _______ me two days to finish the work.
A. took B. cost C. spent D.paid
解析： A It takes sb. 时间 to do sth.
3.This dress looks beautiful on you. How much is it?
It _______ me more than a thousand yuan.
A. cost B. took C. paid D. spent
解析： A 这里的"It"指代 dress，物作主语，用cost 物 cost sb. 金钱
4.----I _______ 5000 yuan on this iPhone.
---- Wow, so much! I can't afford it.
A. cost B. took C. paid D. spent
解析： D 主语是人 ，然后这里的介词是 on, 对应 “人 spend 时间/金钱 on sth.” 这条原则
