What does the boy suggest stopping to buy?

W: Thanks for picking me up this evening, John.
M: No problem, Mom. I’m happy to do it. By the way, I had some friends over after school today and we drank all the milk.  Shall we stop at the supermarket on the way home to get some?
W: I think it is closed by this time of night. But we can stop at the convenience store. They are open 24 hours.
M: Here we are. But I don’t think I’ve been here before. Let’s go in.
W: I don’t come here often because the prices here are higher.
M: There isn’t much selection, but that makes choosing easier.
W: Dose it? I enjoy comparing so I can get the best bargain for our family. Of course, this time we don’t have much choice, do we?
M: No, I guess not. This probably is the only place open at this time of night. Look at this, Mom. They have hamburgers ready made. All you have to do is heat it by microwave for thirty seconds.
W: I know that, John. But they cost more. You’d better go over to have a look at the magazines. It’ll take your mind off food. I’ll take them to the cash counter.