What I get for that money is luxurious; I only use maple syrup for sweetener, fancy grains and lentils, halawi dates as my main winter fruit, and fairly expensive nuts. For veggies I mostly eat cabbage, beets, sweet potatos, and squash which are low cost but delicious (lettuce is such a rip off, particularly considering it lacks any nutritional value). I don't eat as much fruit as I should but I think the model diet in your [1] link has it about right in terms of healthy fruit consumption (that is about 4-5 pieces of fruit per day; 300g of apples is more like 1.5 apples). I think you are right that it is common to not eat particularly healthy, although I think a fair number of people do eat that much fruit (fresh orange juice with breakfast for example). I think I grew up eating about that diet (but a wider range of veggies) before I became vegetarian then vegan and I think it is fairly common. 2.4 eggs a day sounds about right for many people too as I don't think it is uncommon to have an egg or two for breakfast and all sorts of stuff is commonly made with eggs.
I think you are right that for many people these days the cost of eating out is a major part of food costs. I'm surprised that people are spending as much on food away from home as food at home these days (your [2]), although considering food away from home is often quite a bit more expensive it is still going to be less than half of all food and I'd guess a large part of that will be meals during working hours.
In my experience, the number of calories does not as directly relate to the cost as you might think since high calorie grains are usually inexpensive (particularly wheat). Even for non-vegans a lot of the higher calorie diet will be wheat or other grains (or oil or sugar, which are also inexpensive). Although too much maple syrup or expensive nuts can certainly add to the cost :/.
> 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...