You must be talking out of some disillusioned perspective, do you understand the food stamp allowances? Do you understand how living in American outside the realm of hacker news is not 401k plans and stock options. People are actually having problems surviving. This does fix that problem, the cost of labor and transportation is removed from the equation and is just a matter of making money on water and chemical. This can really fix a problem of affordable and sustainable agriculture in America.
tptacek understands this problem as he is/was in Chicago, which has had issues with "food deserts" where poor regions of the city do not have grocery stores within a reasonable commute. And the grocery stores in those poor areas are often overpriced for exploitive reasons.
So tptacek is correct that a farm inside a grocery store does not solve grocery affordability for the poor, because the problem is due to transportation/access, not the cost of the goods.
The bridge between these two views would maybe be if there was a solution of vertical farming that used little real estate and was able to set up a vertical farm in a poor area and had minimal real estate footprint/low rent costs.
How about we just build grocery stores where low-income people can reach them? Farms produce vegetables more cost-effectively than low-income people or retail outlets. This is a solved problem.
I'm not sure if you shop mostly in Whole Foods or buy individually plastic-wrapped bell peppers at Trader Joes, but go to a Mexican grocery store some time and fill a cart full of green things. Vegetables are very cheap.
