You arbitrarily picked the midle tertile. There is a much bigger difference in lifestyle between the 33rd and 67th percentile or the 90th percentile and the 99th percentile than there is between the 67th percentile and the 90th percentile.
I would argue that wealth is a better measure of class than income anyway. There is an inflection point on the wealth curve, which (when you cross it) all you need to is not screw up really badly, and you will be wealthy for the rest of your life.
Yep, at about 2 million dollars you could go to a small friendly town buy a house there and have an income close to the median (and have your assets track with inflation) assuming you can get a 5-6% return on investment, not at all unachievable on 'safe' long term investments. This is all without doing a single hour of work after hitting that point.
I would argue that wealth is a better measure of class than income anyway. There is an inflection point on the wealth curve, which (when you cross it) all you need to is not screw up really badly, and you will be wealthy for the rest of your life.