“Is it realistic for someone just starting one’s working life (or in graduate/professional school) to expect to have the probably higher living standard that his/her parents have in their middle-to-late-career peak earnings years, unless the parents are in much lower paying careers?”
I think you know the answer already, ucb.
There is a difference between affluent middle-to-late career parents doing nice things for their kids, and affluent middle-to-late career parents giving their kids the SAME LIVING STANDARDS that the kids just came out of - which might include a big home in the suburbs, trips overseas, etc.