In the city you could just buy food as you needed it. Your kids could get a gallon of milk at the store in the morning and chug it on the way to school. Same for the eggs. You would just pop over to the egg man who would quickly prepare you a 8 egg omelette and side order of quiche.

When you have more than a couple people in a house, this would mean shopping continuously. And the quantities you'd need for a single day would be more than you could carry effectively without a trunk. (I moved to where I am from a dense city with transit too, it makes more sense for me to be in a smaller city where my kids have a yard to play in and space to plant a garden than to live in a dense urban environment)

In this case I would suggest trying out grocery delivery services like Ocado in the UK.

>> You would just pop over to the egg man

His name was Yauch.

and how much all that will cost vs buying in bulk.

this is incorrect. A significant proportion of high density environments include people living well below the poverty line. In New York City, they shop at places called "bodegas". They often have access to public assistance like food stamps, but they are otherwise consuming those products at "high density" prices. They dont buy in large quantities for financial reasons but also for the "high density makes quantity buying largely impractical" reasons I mentioned above.

doable with a cargo bike as well fwiw;

I myself am doing fine with one or two backpacks a week (on the way home by bike). 2-3km distance to supermarket

When I was living 200m away from a supermarket, I used to buy spontaneously when I wanted to cook something