Elon Musk has suffered one of his darkest days financially, losing about $27 billion in his net worth. As of Thursday's close, the Tesla and SpaceX boss was still the world's richest man, with an estimated net worth of about $388 billion, according to the Forbes Real Time Billionaires List. His net worth remains well ahead of second-ranked Mark Zuckerberg ($236.30 billion) and well ahead of President Donald Trump, whose net worth is estimated at $5.40 billion and ranked 689th on the Forbes list.