No, that is a very common lie told among many fat logicians.
I grew up really poor, I saw my mom going to the ethnic markets or local flea market with all the flies and stretch 20 dollars for 1 week+ of food. Going to Mcdonalds was considered a TREAT.
Then again, as a recent college graduate with $100k in debt. Crockpot, cheap cuts of meat, lentils, rice, beans, potatoes, carrots, and other vegetables. Lunch meats like hotdogs or bologna were considered a TREAT. There was no room for chips, soda, ice cream, cookies, crackers, and other useless matter people put in their mouth. Parents bought me a package of bacon every now and then, I was so happy. Boy, what a time in my life.
Yes, fast food is way cheaper. Sure, a bag of vegetables don't cost that much. But people forget to mention that eating just vegetables isn't healthy. I mean, you have to cook actual meals in order to be healthy. Things like red beans and rice and jambalaya cost way more when you buy the ingredients than when you pick up a bowl from a fast food place.
Fast food is cheaper.
No, you just have to spend your money wisely.