He is now worth 5+ billion and will be president twice. I don't know if your 400 mil number is correct, but I think that is still a pretty good return on investment.
Trump's Net Worth Rose $3.6 Billion This Year—Despite Wild Fluctuations In His Wealth
The past year has been a roller coaster for President-elect Donald Trump—his net worth reached the highest it’s ever been—and fell by just as much.www.forbes.com
Trump did inherit $400 million. His father Fred Trump was also a crooked businessman.
$400 million invested in an index fund in 1985 would be worth $5 billion now...or more.
No one really knows Trump's true net worth. He lies constantly about it just like he lies about everything else.
NY Times: Trump got $413M from his dad, much from tax dodges
NEW YORK (AP) — The New York Times reported Tuesday that President Donald Trump received at least $413 million from his father over the decades, much of that through dubious tax dodges, including outright fraud.
apnews.com