Your body doesn't care about the weight of the food nor the quantity of items in the package.

You eat calories and process nutrients. You can make a lot more meals and a wider variety of recipes with a whole chicken than a pack of hot dogs.

Anyone who shops like you described is not being efficient with their money as long as they have their own kitchen. Poverty is a lot of possible scenarios. I'm not saying they're dumb or anything.

Nutrition is hard to think about when tempted by the modern convenient grocery store with limited money. Unit price has a way of messing with your head. I also get the practicality of having packaged and shelf stable food when you lack access to a freezer and can't stay somewhere for too long. It is what it is.