“I don’t like wasting money,” the frugal 30-year-old tells Fortune. 

Of course, sometimes Guo will splurge: If she’s got a 16-hour flight to endure, she says, she’ll opt for business class. And there’s the odd designer dress hanging in her closet for when she needs it.

“But in terms of like daily life, my assistant just drives me in a pretty old Honda Civic. I don’t care,” she says.

“Everything I wear is free or from Shein…Some of them aren’t going to be that great quality, but there’s always like two pieces or so that really work out, and I just wear them every day,” the billionaire founder says, laughing. “I still literally buy buy-one, get-one-free on Uber Eats.” 

Guo, who is currently the founder and CEO of the creator community platform Passes, adds that a quote she stumbled on on the morning of our interview perfectly summarizes her approach: “It’s like, act broke, stay rich.”

Millionaires need to prove themselves—billionaires don’t

Guo hit the jackpot after the AI startup she cofounded, Scale AI, was reportedly valued at $25 billion in April as part of a share sale. 

Although she left the company in 2018 (two years after founding it), the 5% stake she held on to is now worth an estimated $1.2 billion—making the millennial one of just five female billionaires under 40 according to Forbes’s latest ranking, including Rihanna and Anthropic’s cofounder Daniela Amodei.

It’s why Guo no longer feels the need to prove her wealth with a Patek Philippe everyday watch, or a Hermès Birkin to carry her laptop. That, she says, is the behavior of millionaires.

“Who you see typically wasting money on designer clothes, a nice car, et cetera, they’re technically in the millionaire range,” Guo explains. “All their friends are multimillionaires or billionaires, and they feel a little bit insecure, so they feel the need to be flashy to show other people, ‘Look, I’m successful.’

“I’m not showing off to anyone, right?”

Indeed, for our interview, she’s makeup-free, dressed down, and could pass for any other millennial. But earlier in her career, Guo admits she, too, may have been dripping in designer gear.

“I do think that this is actually something that I personally went through, and I think a lot of people go through when you’re in that middle ground of you’re successful, but not as successful as you want to be. 

“And I think the reason most billionaires dress in a T-shirt, jeans, hoodies is that they can. They don’t need to be in the suit 24/7 because they’re done proving themselves to the rest of the world. The rest of the world is just sucking up to them,” she adds. “And I think that’s kind of how I like feel, where I’m past that hump. I don’t really have to prove myself to anyone.

“No one’s going to look at me and point at me like, ‘Ha ha, she’s so broke’ when I’m pulling up in a Honda Civic because whatever, it doesn’t matter.”

‘Cheap’ CEOs just want to sound relatable—but not Guo

Guo’s not the only ultrawealthy person to admit she’s “pretty frugal.” The world’s most powerful have been boasting about their quiet luxury lifestyle for some time now. They’ve been donning logo-less angora wool sweaters and linen trousers that, to the unassuming eye, could be from anywhere. Experts say their wealthy peers can tell who is wearing Zara from who is in Loro Piana, but the point is to resemble people in lower tax brackets.

Others, like Keke Palmer and Warren Buffett, have been less subtle about how they lead very normal lives, despite their huge net worths—with the world’s most famous investor going as far as to call himself “cheap.”

But in Guo’s eyes, she’s one of the few who actually are as cheap as they say they are. 

“I think that people want to fit into society. Specifically in America, I do think there is a ‘We hate billionaires’ situation. So because of that, people want to show, ‘Look, I’m not your typical billionaire. I’m frugal,’” she explains.

“I’m not saying it to be like, ‘Let me show the world that I’m not like other billionaires,” Guo adds. “I fully admit it, I have gone through that spending spree when I was more insecure, and I felt like I needed to show something.”

And those who really aren’t spending their millions? They aren’t doing it to be relatable, she says. It’s because like her they had their flashy era—then reached the inevitable realization: “Why am I wasting my money on something that doesn’t matter?”