Alan Cole, Lyman Stone, and Richard Borean at the Tax Foundation dug into Bureau of Economic Analysis data to put together a map of where goods and services are cheapest and most expensive. DC is the most expensive, with Hawaii close behind, while Mississippi offers the most savings relative to the national average:
The Tax Foundation is generally of an anti-tax bent, and Cole, Stone, and Borean note that the lack of regional price adjustment in income tax parameters and certain welfare programs means that people in cheap rural areas like Kansas "pay lower taxes despite getting to have a richer amount of consumption" than people making more money in high-cost areas like New York City.
The fact that one can migrate to lower cost areas if one chooses might mitigate this critique a bit, but for low-income people who rely on programs like food stamps without regional price adjustments, and lack the resources to move, it's a real problem. That's also why some advocates for raising the minimum wage like the Center for Budget and Policy Priorities' Jared Bernstein and UMass - Amherst's Arindrajit Dube argue for taking regional price differentials into account when setting minimums.