Americans eat so much processed food simply because it is much cheaper than fresh food. Processed food is made to get consumers addicted (through convenience, taste, etc.) and encourage them to consume much more. Fresh food is almost the opposite.
I grew up in a country where freshly made food is actually cheaper than processed food, even to this day. People who stick to a traditional diet are mostly thin, while those who stick to a processed food diet gain a lot of weight.
I don't understand how people come to this conclusion
Beans/grains/legumes are cheap
Frozen veg is dirt cheap (and retains its nutrition as good as, or better than fresh). In-season fruit and veg
Which foods are more expensive?
People are door-dashing their salaries away and complaining about the price of fresh food...
Convenience and addiction makes more sense, certainly not price
Also, if you are busy single person, basically anything not shelf stable is expensive because you have to buy it in high quantities and it will go to waste if you are not skilled at storage. I, a mature adult, know how to store things, but as a younger person things went to rot a lot from inexperience.
Then there is prep. I spent literally all day on sunday just preparing food for the week. It's about 10-12 hours. That's what 2 hours a day to cook during the week. I have lied to myself and said, "oh, I'll cook something" and then eaten out all day from being busy or being exhausted. To save money stuff I could jam into the microwave was cheaper.
This is how you get there. I cook from fresh vegetables all the time now, but I have the time and energy for it. That just wasn't true at all when I was younger.