Joe Skipper | Reuters The valuation of Elon Musk's SpaceX hit $350 billion based on a secondary share sale, CNBC confirmed on Wednesday. SpaceX and investors agreed to buy stock from insiders in a $1.25 billion purchase offer at $185 a share, according to copies of the offer obtained by CNBC. SpaceX's soaring valuation, ranking well above U.S. defense contractors and among the top 25 in the S&P 500 by market cap, comes as the company furthers its dominant position in the space industry. The valuation of Elon Musk's SpaceX hit $350 billion based on a secondary share sale, CNBC confirmed Wednesday. SpaceX, as well as investors, agreed to buy stock from insiders in a $1.25 billion purchase offer at $185 a share, according to copies of the offer obtained by CNBC. The round does not include raising new capital, as the purchase offer represents a secondary sale of existing shares.