You are assuming access to a grocery store. Disproportionately poor people live in food deserts and have to rely on dollar stores and other things where fruit and vegetables are expensive.

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.