And ditto UChicago, Griffin and the Pritzkers have both donated massive sums (Griffin Dept of Econ, Pritzker School of Medicine)

Yep. It's basically noblesse oblige. At that level and stage of life, the main driver is legacy building ("will I be in the history books").

If someone wanted to live hedonically, you don't need to be a billionaire - a $15-20M net worth would be more than enough.

Those who make the jump from VHNWI to UHNWI have a whole different mindset and viciousness.

JB's philanthropy tends to target Duke and Northwestern (his alma mater).