Adding to your comment, also comparing $10 to $15 is really hard because that could be $10 where rent is $500 or $15 where rent is $2000. Because price levels vary so much nationally we need a way to level those out. It makes little sense to compare people who have fundamentally different purchasing power. Also, IMO, this applies to taxes (why should someone "just making it by" in the bay area, but makes $100k be taxed like someone who pays 50% less for everything they buy in another region of the country)