but the question i have is whether these people who are ultra rich really did provide the value to society that their wealth suggests.
Did bezos or zuckerberg create value? Or did they just extracted the residual value from their employees?
May be instead of a wealth cap, the cap needs to be applied at income (and also make capital gains into income). Your wealth total is uncapped, but you as a person, could not possibly have created more value than $X per year. Where X is set can be debated, but i would expect it to be less than $10mil.
It's really hard to know the alternate history w/o Zuck, but the theory goes that these employees would have been employed in less valuable ways w/o him. Thus there is some marginal value add he brought to the table of which he captures a portion of... Of course all of this is up for debate...
The rationale is that the entrepreneur/organization bringing the greatest value to market is able to subsequently pay employees the most as well and employees will naturally migrate to their greatest opportunity. Whether it's starting their own business, staying at their current job or changing employers/careers it is up to individuals to decide their own best path.
By restricting ultra productive people to a capped return we're effectively disincentivizing these people from providing additional value once they've hit their cap.
additionally you can forsee the fixed per capita cap will be gamed. $250M for me, and for my spouse, and each next of kin, and each parent / uncle aunt etc. Suddenly neopotism is all over the place.