why is fast food cheaper than healthy food?

why is it that fast food is much cheaper than healthy food?

It's true buying healthier foods nowadays is way more expensive than buying a lot of processed junk everyone eats on a daily basis $100 on healthy foods May last you a week or so whereas $100 worth of unhealthy stuff can last you a month. I can't afford healthy food on the basis that I don't smoke and drink but then I don't really have a strict diet since I don't smoke and drink just do more except exercise and it kind of gives me when people call and treat natural food healthy food yes it's healthy but it's not super food it's just the natural food that humans animals have been eating for centuries and is the minimum requirement to a normal lifestyle but then I guess what people mean it's healthier than industrial food...