SpaceX's planned IPO at $135 a share could make more than 4,400 current and former employees millionaires. The public listing could also widen retail participation and trigger fresh spending by long-time equity holders.

The upcoming SpaceX IPO stands to make Elon Musk a very rich man. But it could also make SpaceX employees, even the company’s cafeteria workers, rake in big moolah and become millionaires.