Circa 1990, Mark Cuban was dining with friends. He'd just sold his first business, MicroSolutions, to CompuServe for a reported $6 million.
So Cuban's pals had question: "They asked me what I wanted to do with the money I just had gotten," Cuban tells CNBC Make It.
It was a question Cuban had thought a lot about. Since founding MicroSolutions seven years earlier at age 25, he'd been solely dedicated to work and had gone all those years without a vacation, according to his blog.
"I gave up a lot, personally, early on to try to accomplish my goals," Cuban said on "The Thrive Global Podcast," "knowing that if I ever reach the levels of success even close to where I ended up, I was just gonna have fun."
By the time of the dinner, Cuban had decided it was finally time to do just that.
So Cuban pitched an idea to his pals: "I told them I wanted a lifetime pass on [American Airlines] so I could go anywhere anytime," Cuban tells CNBC Make It.
In 1981, American Airlines introduced the lifetime unlimited AAirpass, a ticket to fly anywhere as often as you wanted — for a steep fee. The passes cost $250,000 when they were introduced, according to the Los Angeles Times, and buyers could shell out another $150,000 to add a companion pass. In 1990 the pass cost $600,000, including a companion ticket. (For comparison, that amount in January 1990 had same buying power as $1,175,293.56 in March 2018, adjusting for inflation.) In 1993, the price increased to $1.01 million, and by 1994, American stopped selling the unlimited passes — perhaps because one owner of the pass flew over 40 million miles, according to the Los Angeles Times.
But Cuban had decided globetrotting would be a fun way to spend his windfall.
"We were at an old school steakhouse that had phones at the tables," Cuban explains to CNBC Make It. "So I used the phone to call [American Airlines] and asked them if they sold life time passes.
"All my friends were drunk when I bought it," he adds.
The paperwork showed up a few days later. While Cuban says he doesn't remember exactly how much he paid nearly 30 years ago, he figured it to be a smart investment at the time.
"I guessed/calculated that my predicted cost per mile would be 12 cents," he says. "That was a good deal to me. So I bought it."
Today, only a few dozen people still own an unlimited pass, according to an American Airlines spokesman, and they are still valid.
But at the time, the splurge was one of the "most fun, best business decisions I ever made," Cuban tweeted Monday. He used the AAirpass "to go party like a madman," he says on the "Thrive Global Podcast."
"I don't know the number," he tells CNBC Make It of the countless trips he took. "I went everywhere."
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Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank."