Neuralink's valuation has surged in just over a year. Here's what's driving the frenzy.

Demand for a piece of anything related to Elon Musk is booming.

The near-trillionaire's brain chip startup, Neuralink, is being valued as high as $42 billion in recent secondary market transactions, according to correspondence seen by Business Insider and a person familiar with the matter.

That's an almost five-time increase from Neuralink's last funding round last year, when the startup raised at a $9 billion valuation, Semafor reported at the time.

According to private markets research provider Caplight, transactions in recent months have ranged from $29 billion to $42 billion, with some current bidders even attempting to buy shares at an almost $60 billion valuation.

Neuralink's soaring secondary-market valuation reflects investors' growing appetite for a piece of Elon Musk's AI and robotics empire. Following SpaceX's blockbuster IPO, private investors are increasingly willing to pay steep premiums for access to Musk's remaining startups.

Because Neuralink is a private company, some investors buy shares via secondary markets, where stock is sold by employees or early investors. These valuations are estimates based on demand rather than continuous public-market prices.

Neuralink didn't respond to a request for comment.

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Musk has earned a reputation for making private investors money, partly by combining his businesses. Investors in X and XAI were able to eventually obtain shares in SpaceX via those acquisitions. One venture investor said that several of their limited partners have been asking to buy Neuralink shares "at any price."

Yet there's hardly a consensus on where Neuralink should trade, with some investors balking at the price of these transactions.

Neuralink is one of Musk's most futuristic companies. It builds brain implants designed to help people with paralysis control computers with their thoughts, and eventually restore their eyesight. That plan is still early, with the chips implanted in 21 trial patients so far, the company announced earlier this year.

Neuralink's official valuation and whether it's raising a new funding round aren't clear. The most recent publicly announced investment came this May, when the sovereign wealth fund of Oman revealed it had invested in Neuralink at an undisclosed valuation.

Musk's wealth is soaring thanks to SpaceX's IPO last month. SpaceX is currently valued at about $1.6 trillion in public markets.