We're about the same age and I remember being able to find enough loose change in my dad's pockets, the car seats and sofa cushions to get to McDonalds almost any time I wanted to. The regular hamburgers, they were small but hey I was a kid and and weighed 80 pounds, those were 20 cents, with cheese 25 cents, I'd get two of them, small fries were I think 20 cents, maybe even 15 cents, and a drink - all for less than a buck.
So like you I thought man fast food prices are so high today, I went and looked for how much the meal I ordered hundreds of times in the early 70's costs today.
Regular Hamburger $1.31x(2)=$2.62
Small French Fries $1.56
Medium Soft Drink $1.69
--------
Total $5.87
Then I went to Google to find an inflation calculator - used
.90 cents in 1972 and according to the inflation calculator
today that is $5.13. Not a big difference. They didn't even have the Quarter Pounder then, all McDonalds had was the small hamburgers/cheeseburgers, the Big Mac, french fries and hot apple pie and soft drinks/milkshakes.
TacoBell was the cheapest, even as an adult in my 20's and I think 30's, the tacos were 39 cents, hard to beat that. I had the misfortune once to see a kid bring in the TacoBell 'meat' in a clear plastic bag - a huge bag of gray mush. I wish I had never seen it. The Arby's roast beef 'product' is gross if you see a photo of it, which shocked me because when I look at an Arby's sandwich it looks like thinly sliced roast beef - it isn't
But penny candy really was penny candy, in fact a lot of the penny candy at the convenience store I spent way too much time at was 2 pieces of candy for 1 cent, depended on which candy. Double Bubble and Black Cat gum was 2 cents apiece.