Around 2009, Resy co-founder and serial entrepreneur Gary Vaynerchuk invested in multiple companies that later became household names: Facebook, Twitter, Tumblr, Snap and Venmo, according to his website.

But despite the chance, he posted on LinkedIn last week, he chose not to invest in Uber — a company that's now worth roughly $138 billion. It was "one of the greatest mistakes of my investing career," wrote Vaynerchuk, currently the CEO of Vaynerchuk Media. "I was literally in the room when Uber was invented. And yet I still passed on investing in the angel round ... twice."

In 2009, Uber's co-founders sought funding at a $10 million valuation, serial entrepreneur Mark Cuban told Peacock's "Hart to Heart" last year. If Vaynerchuk had invested $25,000, as he did with other investments at the time, his money would be worth roughly $345.1 million today, based on Uber's current market capitalization.

Vaynerchuk was friends with Uber co-founders Travis Kalanick and Garrett Camp, but opted out of the company's angel investment round because he wasn't confident in Uber's direction, he told CNBC Make It in 2019.

Kalanick and Camp were maintaining full-time jobs elsewhere while trying to build their startup, and Vaynerchuck had seen two of his own side hustles fail — so he was skeptical Uber would succeed, he told the "Impaulsive with Logan Paul" podcast in 2022.

He changed his mind two years later, after the Uber founders asked him and his brother AJ Vaynerchuk to test the app, he posted on LinkedIn. AJ took the first Uber ride in New York City in 2011, and Vaynerchuk had an epiphany, he wrote.

"I realized, Uber doesn't sell transportation ... Uber sells us time," Vaynerchuk wrote. By allowing people to hail cabs with their phones "there's less friction" getting to where you need to go.

"People value time over everything," he added.

Vaynerchuk isn't the only investor who regrets overlooking Uber: Cuban said he turned down a chance to fund Uber at that $10 million valuation, despite investing $1.7 million in Kalanick's previous startup, a networking company called Red Swoosh.

Cuban loved the idea of an app "to replace taxi cabs," but wanted to invest at a $5 billion valuation instead, he said. Kalanick never replied to the counteroffer, Cuban added.

"Just think: If I would've given him $250,000 on a [$10 million] valuation, it'd be billions," he said.

Disclosures: CNBC owns the exclusive off-network cable rights to "Shark Tank," which features Mark Cuban as a panelist. Peacock is the streaming service of NBCUniversal, the parent company of CNBC.

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