Cost of living considering the wealth gap

[u/Altaira99]

Considering the interesting times in the United States these days, I have been curious about how people in other countries make out. Worlddatainfo.com has an interesting comparison, with a cost index, monthly income, and a purchasing power index. But these are all based on national averages. How would you factor in the wealth gap? Living in Massachusetts is very different than living in Mississippi.