"What is inflation?"

Using duck's feet to knead the dough doesn't seem hygienic. Also i'm assuming half-bang didn't know she could just go into the kitchen and make her some cookies.

Half-bangs must be concerned that the other girls will crash the economy. They are basically printing money.

This seems to imply to me that they've been eating store bought cookies the entire time. Seeing as how they have so much, they probably also just bought the cheap no name brand bulk boxes too.