I spend less than $3 per day for a healthy diet (high calorie for high altitude, extreme cold and the like). Careful planning, buying in bulk and real cooking are required (baking all bread at home, etc.). No soda pop. No salt-filled Ramen noodles. Avoid sugar. Think proper food groups and a varied diet (’60s style).
I was fine with your comment until the "'60s style" aside. The thing I remember most about eating in the '60s as a kid was when my dad worked 4-midnights (he was a cop) and mom was in charge of dinner - hamburger and tuna helper and tuna potato chip casseroles was the norm, unless there were leftovers from the Sunday roast my dad or grandmother (mom's mom) had cooked.
My mother actually had to learn how to cook, starting when her mother moved to Florida in '73 and really had to learn when I moved out in '82. She thought it "quaint" when I would send or bring her food stuffs I had grown, cooked and canned myself, but she also loved when I would come to visit because she knew I would take over the kitchen and do all the cooking while there. My dad appreciated and enjoyed it, my mother expected it.