I can cook food for a whole day for about €1. It will mostly be potatoes and lack any nutrients, but it will be a lot cheaper than any processed food I could buy. Or I can cook something with fresh ingredients and lots of fiber and nutrients, but those ingredients are expensive to buy in part because handling time sensitive squishy stuff makes every step of the supply chain more expensive.
Processed food in the USA is very expensive. Frozen pizza, chips, cookies, frozen dinners, cereals, etc can cost more than Grass Fed Organic beef per lb. We have a Grocer called Sprouts that has Grass Fed Ground Beef for $2.99lb USD. A frozen pizza at Walmart is 4.99 USD. A bag of Potato Chips is $2.99 at Walmart.
If you get a chance check out any USA Grocery flier and you will be shocked at how little real food costs.
But as a european (french) guy I must say that I was very surprised, when visiting 2 weeks in Brooklyn, to find that grocery was not as expensive as I was expecting. At all.
You are totally right.
We could eat real meals every night after a tourist day, for around same prices than in France.
https://www.dochara.com/the-irish/food-history/food-in-irela...
"The burgeoning population lived on a diet comprised mainly of potatoes and milk, which if eaten in sufficient quantity is a surprisingly nutritious, if monotonous, diet. It is also relatively tasty and easy to prepare."
The advantage of potatoes is that there is a large number of recipes that consist almost entirely of potatoes (mashed potatoes, hash browns, roast potatoes, boiled potatoes, potato chips, etc.) so there's a lot of variety in a fixed budget.
Rice ultimately is cheap only because of labour costs. It takes tons of water to grow.