SpaceX Share Sale to Value Musk’s Firm at About $400 Billion (1)

Elon Musk’s SpaceX is planning an insider share sale that would value the company at about $400 billion, according to people familiar with the matter.

The deal marks a rapidly climbing value for Musk’s rocket and satellite maker, and cements SpaceX’s status as the most valuable private startup in the world.

The per-share price of $212 is up substantially from the $185 set in a prior transaction that valued SpaceX at $350 billion in December, said the people, who spoke on condition of anonymity because the matter is confidential.

A SpaceX representative didn’t immediately respond to a request for ...