Earlier quoted context omitted.
> most will probably become wealthy again. Source?
There's a book that attempts to look at this called, "The Son Also Rises." It tracks wealth by surnames and argues that the ability to gain (or regain) wealth is inheritable. This thesis is in contradiction to some of the ways I've experienced the world, but it is a source supporting the parent's claim. For my own political inclinations I'd be happy to hear many others that support the opposite claim.
https://press.princeton.edu/books/hardcover/9780691162546/th...
https://archive.org/details/CSPAN2_20151004_190000_Book_Disc...
https://www.worldcat.org/title/son-also-rises-surnames-and-t...
http://gen.lib.rus.ec/book/index.php?md5=76BC054612F39ED6CBD...