No, I don't "seem" to be doing anything of the kind.No, you seem to be assuming that the rich would live with a "minimum standard of living" comparable to the poor.
The poor must. The rich choose. It's the key fact of the matter.You keep saying that. Just noise.
As far as cheaper stores often missing from poorest neighborhoods: https://en.wikipedia.org/wiki/Food_desert
Also competition between stores. (In wealthier neighborhoods I've seen people shopping in pairs, separate stores, comparing prices by phone.)There's the same competition for both bargain and premium brands?
Right next to the lower quality, lower priced brands - and holding down the prices of those brands. The rich choose.More choice usually means higher quality, and priced, brands.
Incompetence is not a requirement of the calculation. If one is comparing the differences in the minimum cost of living for different economic classes, the differences in what they have to pay for and what they have to pay for it must be included, no?Not factors in the coat of living calculation.
Rich people can even buy online, and have low priced stuff delivered to their doors. Poor people meet obstacles doing that - from credit cards and computer access to financial and package security - and these obstacles add cost.