This doesn't respond to the main point of your comment (the livability of a $6k a year for a family of four), but I think it's interesting anyway.
> feeding a family of 4 should cost around $20k
This sounded absolutely crazy to me, so I did a little bit of digging. $20k is $416 per person, per month. For reference, we (a family of two adults) spend less than that total per month on groceries - not including eating out, which we do a couple times a month. That's been relatively constant, it was ~20% more or so when we lived in a much more expensive city (typical rent more than double our current).
I would be really interested in hearing concrete stories from other middle class or poor people (or seeing links), but the relevant points of difference seem to be these:
* The cost estimates are based on a 2400 calorie diet per person. Both of us eat less than that as adults, and 2 children can certainly be expected to do so.
* The food estimates they're using [1] seem outlandish. It includes no processed foods, has you eating apples, bananas, oranges, and tomatoes every day, and the weights given are strange as well - 300 g of apples is probably two apples, so we're talking a lot of fruit in this meal plan. It also estimates eating 2.4 eggs per day??!
* It's not clear how the average values for the whole U.S. are derived. If only large cities are considered, the cost will probably be artificially inflated relative to the true average.
* We're both vegetarian, and a considerable fraction of our food is made fresh. Even with the US government heavily subsidizing meat purchases, it's probably significant cost savings for us to live like this.
* In the other direction, I don't think grocery cost is likely to account for anything close to 100% of the true cost of "feeding a family of four", because it doesn't account for eating out, drive-through coffee purchases, etc. Americans spend more on food away from home than they do food at home. [2]
In terms of food cost estimates that are not based on the grocery cost of an arbitrary (and odd) subset of the food that people eat, I found the following estimates:
* USDA: the middle quintile household spends $9k a year on food (with the lowest quintile around $5k). [3] $20k a year would be more than spent by the average household in the highest quintile. (Note: this is for a typical household, not a family of four. On the other hand, this includes realistic not-at-home food expenses.)
* The USDA offers food plans that are intended to be healthy (so likely more expensive than typical American food choices). On a "thrifty" budget (the lowest level), their costs for a reference family of four are $975 a month, or $11.7k a year. [4] Even on the most liberal plan provided [5], the cost for the reference family of four is $19k.
[1] https://www.numbeo.com/food-prices/country_result.jsp?countr...
[2] https://www.ers.usda.gov/data-products/ag-and-food-statistic...
[3] https://www.ers.usda.gov/data-products/chart-gallery/gallery...
[4] https://fns-prod.azureedge.us/sites/default/files/resource-f...
[5] https://fns-prod.azureedge.us/sites/default/files/resource-f...