Mark Cuban put $500K into a stranger’s company. It’s now a SpaceX competitor worth $4 billion

He once bought a $25 million Dallas mansion sight unseen, calling it his one “why the f–k not purchase.” But one of his most lucrative gambles started even more casually: with a cold email from a stranger he says he’s still never met.

Speaking in a September 2024 interview with podcaster and comedian Theo Von, Cuban recounted how a young entrepreneur named Tim Ellis—who was also an ex-intern at Blue Origin (Jeff Bezos’ space company) — and his friends emailed him from Dallas, saying they wanted to start a space company. Cuban admitted he had no relevant expertise, but wanted to give them a shot anyway.

“I don’t know shit about space, but I’ll get you started and see what happens,” Cuban recalled telling them. 

That company was Relativity Space. Cuban said the entire relationship played out over email, and he’s still never met Ellis in person. 

“It was all email, never met him,” he said, but still gave them $500,000 to start. “Now I’ve invested a few million, [and now] they’re worth $4 billion,” Cuban said.

At Blue Origin, Ellis started the metal 3D-printing division before founding Relativity, he told TechCrunch—so Cuban was quick to credit the founders for the success of the business rather than himself. 

“It’s not like I helped them get there,” Cuban said. “These guys were just insanely smart and good. I got lucky … I just got him started.”

What Relativity Space actually does

Relativity’s pitch is manufacturing disruption: The company 3D-prints the majority of its rockets, aiming to slash parts counts and production time.

“In the end, they’re getting better performance and lower costs, which means we can potentially fly our payloads and astronauts safely and at a reduced cost on some of their missions,” Paul Gradl, principal engineer of component development at Marshall, told NASA. 

Relativity is developing Terran R, a medium-to-heavy-lift, fully reusable two-stage rocket designed to compete with SpaceX’s Falcon 9, with a first launch targeted for late 2026.

The company has changed considerably since Cuban’s early bet. After cash-flow challenges in late 2024, former Google CEO Eric Schmidt took over as CEO in March 2025, making a significant personal investment and taking a controlling interest; Ellis remains on the board. 

Relativity is now valued at roughly $4 billion and has amassed more than $2.9 billion in orders with customers including NASA, the U.S. Space Force, SES, Intelsat, and OneWeb, according to TSG Invest. Executives have framed this demand as customers “voting with their checkbooks” for an alternative to Elon Musk’s SpaceX.

Relativity’s backlog “shows how desperate the market is for another cost-effective launch services provider” given the dominant position of SpaceX, said Josh Brost, chief revenue officer of Relativity, according to SpaceNews.

“Coming for you, Elon,” Cuban said.

SpaceX, meanwhile, is in the middle of the most anticipated market debut in years. The company filed to go public and is expected to list on the Nasdaq around mid-June 2026, in what could be the largest IPO of all time. SpaceX is reportedly targeting a valuation of more than $2 trillion.

Mark Cuban’s pattern of betting before looking

The Relativity is a solid example of how Cuban often operates. After all, he bought his Dallas mansion without ever setting foot inside, telling GQ he’d seen only photos before committing. His instincts aren’t so much recklessness as a willingness to act on conviction and let smart people and favorable terms do the work.

“I’ve done a bunch of deals from people just cold emailing me,” Cuban said in the interview with Von.

Cuban, who is worth an estimated $10.3 billion, made his fortune by selling Broadcast.com to Yahoo for $5.7 billion in 1999 and later turned a $285 million Dallas Mavericks purchase into a multibillion-dollar return, retaining a minority stake after the sale. These days, his most visible venture is Cost Plus Drugs, the generic-pharmacy company he co-founded in 2022 to undercut traditional drug prices.

His takeaway from the Relativity deal was simple: “Sometimes just making yourself available opens a lot of doors. And it’s helped me a ton.”