It's on me.我来出钱。/我请客。

A: Order what you want. It's on me.

想吃什么尽管点，我请客。

B: That's very nice. I guess I'll get the steak.

太好了，我想吃牛排。

How much do I owe you?(餐馆、商店等)多少钱?

A: You never paid me the money I lent you.

欠我的钱，你一分都没还呢。

B: I'm sorry. How much do I owe you?

不好意思，欠你多少来着?

(This is) My treat.我来请。

A: How much is the restaurant?

这顿饭多少钱?

B: Don't worry about it This.

别担心，我请你。