Taking a subset of statistical average income is not the proper way to define the "Middle Class." It's better defined by what you can achieve with a specific income. Can you afford higher education both for you and your offspring? Can you afford to own your home? Can you afford reasonable and convenient means of transportation for your area (multiple family cars in rural areas, but maybe one or even none in urban ones)? Can you afford occasional leisure activities? Can you afford to have a savings and retirement account? Do medical expenses not worry you?

Meeting most or all of these requirements is what sets people into the middle class. I agree with the article that this number is different as you need to take into account local cost of living, but a lot of these requirements are not tied to local costs. I also think this probably puts this number at a higher point than many people think. I have many friends that think, "Oh, I make $20/hr. I'm middle class now!" And I don't agree. You're still going to struggle with bills at that level of income. Middle class is about being above that struggle most of the time. There's a freedom that comes with not having a loan for your education, vehicles, emergency spending (credit cards), etc. And a middle class family should have that freedom.

I don't know that I can see $250k being middle class still, but I do think in the SF Bay area, a family making $150k is quite reasonably still middle class. The upper bound of the middle class is I think harder to define than the lower bound. Once you always have the option of not working for long stretches of time (more than several months) that might be a good indicator of upper class.

I think throughout the last 40 years or so we've gradually become so accustomed to the diminishing size of the middle class. We don't realize what it used to mean. We forget that a time existed where a family with a good budget could live on one income and still afford a house, two cars, college funds for the kids, vacations, and savings.