Anyone who's posting that food is getting cheaper must be buying some shitty food.
We buy almost *no* processed foods at all - and the price of real, regular food has skyrocketed in the past 3 years. Since I don't buy it, I'm unsure, but yeah maybe it's cheap to buy a plastic bottle full of high-fructose corn syrup chemical water, or a frozen package of lab engineered corpo-farmed quasi-chicken nuggets, but if you go buy the *real* chicken - not the one that's been frozen and shipped to China for processing ala Wallyworld - you'll see that prices are quite a bit higher than they were a few years ago.
My house spends about 20% of take-home pay on food. I know this because I keep a detailed budget every month. Very, very little of that is spent outside the house at restaurants - 90% is on regular bought, non-processed food. I have no idea if that's cheap, or expensive, compared with the past, but I do know that it's cheaper to eat Ramen Noodles than Broccoli. You can eat a shitload of ramen noodles for every head of broccoli you can buy. We eat meat at dinner probably 5 out of 7 days per week, so if we ate a little less meat we could trim that number slightly - however, that meat makes 2 meals, since it's only part of a dish and not the dish - like spaghetti with meat, or chicken, vegetables and rice, etc. The leftovers end up being the following day's lunch. I'm too damn stingy with my money to be tossing out food. Scraps are composted for the garden.
It's really no wonder poor(er) people in the US are fat, and getting fatter - the quality of the food they can afford to buy is piss-poor.