Many people don't have any real understanding of how wealthy people have been in the past. The Walton family is a fun case. Split the fortune among the family and there are still billionaires in the mix.

Edit: should add that Elon is still valued at a good percentage of the US gdp. So, not unreasonable to say that is incomprehensible, as well. By that measure, is similar to Rockefeller, I think.