Well, I admit, I have no clue about MURRICAN prices on vegetables like carrots, potatoes, onions of different kinds and stuff.
So, yea, maybe it is the other way around than it is in Germany. But here, you can easily prepare a proper soup with some animal fat in it for like 5€ which ends up being a good lunch for 3 days at least. If you don't wanna eat it for 3 days, just prepare it and freeze potions of it for the next week or something.
It's actually more of a social issue in Germany that low-income families tend to eat fast food over self-prepared food. Most of the times it's not a time issue... Different story.
Besides, I am not talking about some silly sporty health food. Normal rice is good enoug, normal pasta does the job, so does normal yogurt...