(Reuters) - Tesla CEO Elon Musk's net worth crossed $400 billion on Thursday, the Forbes real-time billionaires list showed, boosted by a nearly 71% surge in the automaker's shares this year and the soaring valuation of his rocket company SpaceX.

Musk is Tesla's largest shareholder with about a 13% stake in the company. The EV maker's shares rose to a record high of $424.9 on Wednesday, extending a rally that kicked off following the Nov. 5 election.

His net worth was also boosted by an insider share sale of SpaceX, which Musk heads. The rocket company and its investors agreed to purchase as much as $1.25 billion of its common shares, Bloomberg News reported on Tuesday.

"What's really crazy about this is that almost no investors wanted to sell shares even at a $350B valuation!" Musk wrote in a reply to a post on X referring to the Bloomberg report.

He added that SpaceX has reduced the number of shares it bought back from employees in order to bring in some new investors.

Tesla investors have pinned their hopes on Musk's relationship with President-elect Donald Trump, hoping the billionaire's role in shaping the incoming Republican administration's policy agenda would benefit the automaker.

Besides Tesla, Musk also heads brain technology startup Neuralink. Both SpaceX and Neuralink rely heavily on government regulation and policy and could benefit from a business-friendly administration.

Musk, who spent over a quarter of a billion dollars to help Trump win the election, also owns social media site X and tunnel builder The Boring Company.

Musk is followed on the billionaires list by Amazon founder Jeff Bezos - with a net worth of $243.7 billion, while Oracle co-founder Larry Ellison is in the third spot with a net worth of $223.4 billion.

(Reporting by Deborah Sophia and Rishi Kant in Bengaluru; Editing by Krishna Chandra Eluri and Anil D'Silva)