I'm not defending it nor am I saying it's typical, but it's not that hard to spend $500 per person per month on groceries.
It's definitely doable (and then some) for folks living in high cost of living places. I recently went on a quick weekend trip to such a place. I knew I didn't have the type of money to dine out, but I figured I could suffice on a few staples from the grocery store. I visited several different stores, and the prices were all about the same (i.e. insane). The little pint (or half pint?) Ben and Jerry's was $10 - 12. A container of romaine lettuce was $8. A package of Oscar Meyer sliced deli meat was $15. These prices are easily 3 - 4 times what they typically cost where I live.
Also, a lot of people shop at the kinds of stores where you can find everything from apples to Apple watches. And when people do their "grocery" shopping, they're buying bulk paper towels, a case of wine, a new Switch game for the kids, cosmetics, cat litter, clothes, 30 pack of batteries, a couple azaleas, and a partridge in a pear tree and then calling that their grocery bill. So, it's not exactly a fair label nor an accurate assumption that the grocery bill is just groceries (i.e. food).
And honestly, if you mean HOW as in how can they afford it: $500 x 4 = $2,000 or $24,000. A lot of money, sure, but median household income (in the USA) is like $80,000 and I'm guessing that $500 a month per person is above median expenditure (especially if we're excluding the folks that like to include the partridge in their grocery bill), so most people spending that much on food would be earning way more than median income.
Nice try Steve.
Remember that time I discovered a major bug in Reddit that I reported dozens of times to the site's feedback form and directly to your user account but I never got a response about and it never got fixed (until I used the exploit in a way that directly affected you)? Well, if that rings a bell, then guess what? It's me again. Toodles.