$240,000 in Bay Area California is immensely different than $240,000 in the hills of West Virginia. Middle class is more of a lifestyle than a particular income number. It is entirely possible that middle class in a particular city includes people whose incomes are in the top 5% nationally, but still live barely comfortably because their high cost-of-living area.

I'd argue median income is irrelevant when it comes to assessing whether or not someone is living a middle class lifestyle.