Typical mistake: *Come on, I'll pay you a
You pay a person, you pay a bill,
and you pay sums of money, but you pay for
something you buy.
You can have the room free, but you'll have to pay me £10 a week
for your meals. (房间免费，但每周你要付十镑饭费。)
When we want to talk about paying for a drink or a
meal for a person, we usually use the verb buy (or
Come on, I'll buy you a drink.
Let me get you a drink. （我请你喝一杯）
Can I buy you lunch?（我可以请您吃午饭吗）
for can also express the idea of paying money that
somebody else owes.
Don't worry about money; I'll pay for you.（不用担心钱；我会还你的。）