Soda here is about 50 cents a can; milk is twice that.

People with limited funds will buy soda -- twice the bang for the buck, right?

I understand the source of yr discontent with this couple as an example and I didn't actually read the story. :-) But the obesity/diabetes epidemic in America isn't all about lazy, self-indulgent people making poor food choices; it's also about hungry people buying cheap food.