Flavor does not matter, presentation does not matter but the food shouldn’t make you sick, and should ideally have enough calories per day for the average person to survive (2000 kcal min).
Edit: I am not in any danger of starving or malnutrition, nor am I insolvent. I’m mainly asking this question out of curiosity on how people would approach a solution :)
The main goal for MREs isn’t to be cheap, it’s to be nutritious, shelf stable, and easy to prepare. There are certainly cheaper ways if your only goal is to be nutritious.
I made some burritos a couple weeks ago. Mainly rice and beans, with some beef, cheese, and salsa for flavor, seasoned to my liking in a flour wrap. The intent was to freeze them for quick meals, so no fresh veggies. One or two of those paired with a salad would be quite nutritious, and probably cost less than $1 each. If I skipped the beef and cheese, it would certainly cost less than $1 each.
The bulk of those meals would be rice and beans, and you can buy them in bulk, but they’re still cheap even if you don’t.