Selling a company for billions of dollars didn’t immediately upgrade Mark Cuban’s life. In fact, the longtime entrepreneur, investor and “Shark Tank” star found himself in the middle seat of an airplane while going to Las Vegas to celebrate his windfall.

“When I sold my company for billions of dollars, to go and celebrate, I was on a Southwest flight,” Cuban told earlier this year. “I was in the center seat facing the wrong way on the plane thinking, ‘This is just perfect.’”

In 1999, Cuban and his co-founders sold their company to Yahoo for $5.7 billion in stock. Instead of letting it go to his head, Cuban said, a simple concept kept him grounded.

“The wisest advice I ever got was ‘live like a student,’” Cuban said. “That served me a long, long time.”

That meant continuing to live a low-key lifestyle, which “took away a lot” of risk and uncertainty in his financial life. In an email, Cuban confirmed that he “didn’t change much after selling my first company” — keeping the same car, house and even furniture.

But Cuban did splurge on one luxury item, which meant his days of sitting in the middle seat didn’t last long: In 1999, he famously went online to buy a private jet for $40 million. His purchase of a Gulfstream V business jet still holds the title for the largest-ever single e-commerce transaction in the Guinness Book of World Records.

Buying a private jet “was my all-time goal,” Cuban told Money in 2017. “Because the asset I value the most is time, and that bought me time.”

Notably, Cuban has also celebrated his financial milestones in ways that didn’t always require large amounts of spending. According to comments he made at OZY Fest in New York City in 2017, he celebrated first becoming a billionaire — in 1998, when went public — by dancing in the nude.

At the time, he was sitting at a computer, repeatedly refreshing a webpage to check’s stock price. “Obviously I knew exactly what the number was to become a billionaire,” he said. ″[The price] gets up there, and then I did my little naked billionaire dance.”

Today, Cuban is the world’s 247th-richest person with a net worth of $4.5 billion.