[twoodfin]

So, the society you just described would be rightfully described as having high social mobility.

But it would just be economic Brownian motion. Social mobility isn't (I hope!) valued because it shows that a society produces random outcomes, but rather that it enables people to achieve to the limit of their talents.

[watwut]

Social mobility is defined somehow and that somehow is not "the absolute total measure of fairness of any society". And speaking about virtually any country in the world, including North Korea, they all have lower class and upper class. Your worry about totally classless society is purely theoretical.

If we would live in classless society, social mobility would be less important measure.

Plus, you define achieving the limit of the talent in purely financial form. If I am genius mathematician, achieving limits of the talent mean doing great (potentially useful) math somewhere at the university. That does not translate to neither "high class" nor "rich".