Median incomes are 75% higher in the high cost area, but housing costs are 200-400% higher, which, being a major expense for just about everyone, quickly erodes any gains you might make on the income side. Services, like internet connections, were also more expensive in the high cost area. Goods like iPhones are the same in both places, you are right, but is actually a larger portion of your disposable income because of the higher living costs.
The one place you might be able to make gains in the high cost area is if you struggle through paying those 400% higher housing costs with the intent of selling your home and moving to a low cost area later in life. Then you can ride that significant equity you have built, assuming the property maintains or increases in value.
That said, my preferred method is to live in a low cost area and work in a high cost area (telecommute).