Despite their ability to spend, spend, spend, even some of the richest people in the world stick to a few frugal habits. For a few billionaires, that means opting out of Michelin-starred restaurants in favor of an American classic: McDonald's.
Facebook CEO Mark Zuckerberg was spotted eating a grab-and-go McDonald's meal on the Mignanelli Steps near Piazza Spagna in Rome during his honeymoon with his new wife Priscilla Chan in 2012.
Legendary investor Warren Buffett loves the Golden Arches as well. He visits the restaurant every day for breakfast and never spends more than $3.17.
On his five-minute drive to the office, which he's been doing for the past 54 years, Buffett stops by McDonald's and orders one of three items.
"I tell my wife, as I shave in the morning, I say, 'Either $2.61, $2.95 or $3.17.' And she puts that amount in the little cup by me here [in the car]," he explains in HBO's documentary, "Becoming Warren Buffett."
Each amount corresponds with a different option at McDonald's. For $2.61, he can get two sausage patties, $3.17 gets him a bacon, egg and cheese biscuit and $2.95 buys him a sausage, egg and cheese biscuit.
Buffett keeps it frugal even when treating his friends to lunch. In Bill and Melinda Gates' 2017 annual letter, which they addressed to longtime friend Buffett, Bill tells the story of a particularly economical lunch Buffett took him out for years ago.
"Remember the laugh we had when we traveled together to Hong Kong and decided to get lunch at McDonald's? You offered to pay, dug into your pocket, and pulled out … coupons!" he writes.
Both Buffett and Gates are frequent enough patrons to Mickey D's that they've earned the chain's coveted Gold Cards. In a , Buffett shared the contents of his wallet, showing off his card, which lets him eat for free at any McDonald's in Omaha for the rest of his life.
"So that's why the Buffett family has Christmas dinner at McDonald's," he laughs. "It explains a lot of things."
The cards are rare. While Buffett's is only good in Omaha, he explains that Gates' card gets him free meals anywhere in the world. "Mine is only good in Omaha, but I never leave Omaha so mine is just as good as his," he says.
Billionaires aren't the only ones who can boast of Gold Card privileges — although if helps to know someone. In 2015, actor Rob Lowe revealed his own card during a segment on Jimmy Kimmel Live. "My buddy's dad invented the Egg McMuffin," he says. "Which, to me, is like the greatest human achievement."
Like Buffett's card, Lowe's was limited. He could only use it at McDonald's franchises in Santa Barbara or Goleta, Calif., and it expired after a year, in 2016.
Like this story? Like CNBC Make It on Facebook