alt Hacker News> Simple inflation adjustment gives us x but the real price is more or less than x. Why is that?
Restaurant economics are a function of ingredient costs and labour. I suspect ingredient costs are close to OP's estimated multiples. But real wages are way up since the 1950s. Anything with a large labour component of costs will have tended to rise faster than inflation, which is an average of goods and services.
(There are specialised metrics if you actually wanted to dig into this question.)
Are you saying the prices listed were just for the ingredients and not the actual cost to the person ordering? They mentioned they saw the price in a photo which suggest it is what the person would be charged. I get that labor costs would cause an increase of raw ingredient price comparisons for total prices. But if you could pay buy a burger for a nickel but now need $10, there is a definite issue in just a "simple" adjustment that suggests you'd only need $5. If the numbers are that far off because the simple needs to be more advanced, what's the point of the simple numbers? Bad data is worse than no data.