On top of that there's time cost - making healthy meals form scratch takes far more time than making them from store-bought "parts" (eg: to get boiled beans I need to soak them, them boil for hours. For this I need time, more time and a lot of energy)
I think you're not taking the average human's reality.
In '80s in mine we had mostly only healthy foods. Crap sold as food today was completely unavailable; the most unhealthy would be a birthday cake or additional slice of bacon on a plate.
I think I am aware and I posit it's very hard for people on low I comes to even be able to buy a quality food.
The memes you are repeating do not match actual US or world statistics. They do make everyone feel better all around. I.e. even free enterprise and freedom of choice stories work worse when we are genetically tuned to choose ourselves to death and market tuned to profit from it. (A bag of potatoes is far more available globally than decades ago but a bag of doritos has a far more impressive availability increase.)
And you didn't even engage with my main point, it's very hard for people especially on the low income to not just eat but even access healthy foods.
Here is the actual data that says people were spending 50% more on food despite more prep time and lower health food options:
https://www.ers.usda.gov/data-products/charts-of-note/110333
Your point is very socially satisfying but has no accuracy for why the majority of Americans are overweight or why the trend is global. (People buy expensive brand trash food but could in fact afford and find healthier food for less of their income now than in 1980.)
It’s just about the most fundamental law in the entire universe, in fact.