It briefly made Elon Musk the world's first trillionaire, before the stock cooled and his fortune slipped back below the milestone within weeks. SpaceX shares fell 13.6% on Wednesday to $108.27 (£80.44) - well below the initial listing price of $135 a share. Sinead O'Sullivan, an economist who has previously worked for Nasa, told the BBC in June she thinks SpaceX is an "Elon Musk ego project". "You're buying a share of the Elon Musk brand more than any kind of space industry," she said. But Ron Epstein, an aerospace analyst at Bank of America Securities, says the recent share price swings say more about the market than the company.