Anyone in an inner city should be within a mile or two of a street market. When I lived and worked in London, there were a number of them. DD, as a student used to visit Lewisham market after 3.00 on a Saturday and by sacks of veg for £1 or s and share them between her friends.
I do appreciate that not every one will be able to do that, but poor people are just as intelligent as other people and should be able to work these things out.
We are often told that they trail from supermarket to supermarket trying to buy food at its cheapest, and I know from my own experience that that is very time consuming. And people now have very variable working hours, so many are available mid day, mid week.
For those really on the breadline, dependent on Food Banks, and with very limited cooking facilities in inadequate living accommodation, then yes, life is indeed very very difficult and they have very few options, but the vast majority of people are not, thankfully, in that category. There income is above that level, although not necessarily by much
Most, of us on GN will remember the vertigenous inflation rates of the 1970s and early 80s, which almost exactly covers the period when I was either not working because I had young children or in poorly paid part time posts and one learnt, quickly how to plan and contrive to produce decent meals on a small and constantly squeezed budget.