I understand, dear parents, that you want your children to be independent and brave and that they need to learn how to talk to the nice lady at the snackbar counter by themselves eventually, but if you're going to insist on sending them out to get food for the whole gang alone, at least glance over our prices to make sure you gave them enough money first.

It inevitably happens that a small child waits patiently in line, rattles off a huge order to me, and then when I finish it, realizes that he's short money. It happens literally ALL THE TIME. And this isn't just short a few cents or a couple dollars, this kid was short ten bucks. Ten whole dollars. Because his parents failed to realize that this is a movie theater and our prices are jacked through the roof and you sent him out with ten dollars but he ordered twenty dollars worth of food.

And then he stares at me for a minute as if I'm going to magically pull ten bucks out of my ear and give it to him. (The worst part is, some parents try this intentionally, thinking we can't say no to a cute little kid. They're wrong.)

Needless to say, he ran off without any food at all, meaning I had to throw his entire order away. It's a gigantic waste of food, my time, the kid's time, and the time of the people stuck waiting behind the kid.

tl;dr
Don't send your kid to buy food if you don't give him enough money. He's nine, he ain't got a job, he ain't paying for that shit by himself.