I think the realistic number is is more like 2-4% if it’s not supplemented by working (and sometimes even working) I also think when you add in things like paying for private school/ college, divorces, taxes, carrying cost of real estate, etc. luxury travel/clothes/meals/vacations it’s a big number.

I’m not saying it’s not possible, but I suspect the vast majority of grandchildren of a wealthy couple have meaningfully less than the original couple did, as well as less than their parents did.