It would be a ton with ~10% annualized returns on the SNP500 since 1985, especially if you reinvest dividends. Someone who lives very frugally can probably just live off the interest off that 400k alone and if they bank unitl a million, they can have a safe buffer and a comfortable lifestyle. If they reinvest all of it for fourty years since 1985 it’d be worth on the order of $10-25 million.

It’s actually quite stark how bad it’s gotten. I’d rather just give a kid that money to invest and have them live at home doing whatever work floats their fancy until they can live comfortably on interest alone.