These two men paid over $650,000 for lunch with Warren Buffett—here are 3 things they learned

The average American spends just over $1,000 a year getting lunch at restaurants. But investors Guy Spier, 52, and Mohnish Pabrai, 53, spent $650,100 on just one lunch, although it was for a very special reason: They got to dine with billionaire Warren Buffett.

The businessmen purchased their high-priced lunch in 2007 as part of an annual charity auction for Glide Foundation, which helps the homeless and impoverished get back on their feet. Last year, the bidding price topped the million dollar mark—a steep climb from the $25,000 winning bid when the yearly auction began in 2000.

While some may scoff at paying such an exorbitant fee for a 2½-hour lunch, even if it is with Buffett, Spier and Pabrai told CNBC's Squawk Box in 2010 that it was "worth every penny."

"I think we would have been willing to pay a lot more than that," said Pabrai. "Well worth it."

Not only was the experience "fantastic," according to the two investors, but they also walked away with three key business lessons:

During their lunch, Buffet explained how he and his longtime business partner Charlie Munger approach the truth, honesty and integrity. "He and Mr. Munger use an internal yardstick," Pabrai told CNBC.

Buffett gave the men an unconventional method to determine their integrity, asking them: "Would you rather be the greatest lover in the world yet be known as the worst, or would you rather be the worst lover and be known as the greatest?"

"And he said, 'If you know how to answer that correctly, then you have the right internal yardstick,'" recalled Pabrai.

Spier continued, "It's a very interesting person who can walk around, imagine that the world, the feedback that they're getting is that they're awful at what they do, but deep down they know that what they're doing is right."

However, Buffett has long been a big believer in cultivating integrity, especially at young age, and has previously noted that he looks for this key characteristic in all employees.

"A student [of college age] can pretty much decide what kind a person they are going to be at 60," the billionaire said in an interview for the Nebraska Business magazine. "If they don't have integrity [now], they never will."

Warren Buffett reportedly once said, "The difference between successful people and really successful people is that really successful people say no to almost everything." And he clearly lives by this sentiment, Spier wrote in a 2014 article for MarketWatch.

During their "power lunch," Spier said that Buffet showed them his diary, which was almost bare. "He likes to leave his time unstructured, and to leave plenty of room for spontaneity," said Spier.

This isn't a new habit of his, according to Buffett's billionaire bestie Bill Gates. In an interview with Charlie Rose, Gates said that when he first met Buffett in 1991, Buffett showed him his calendar, which was largely empty. This taught the Microsoft co-founder a valuable lesson. "You control your time," explained Gates, who used to have a penchant for packing his calendar."It's not a proxy of your seriousness that you've filled every minute in your schedule."

Years later, nothing has changed for Buffett and the billionaire still credits his "consistently amazing growth" with this ability to say 'no.'

Spier pledged to do the same after his lunch with Buffett. He wrote for MarketWatch: "Observing Buffett, I could tell that even though he is a kind man at heart he also has absolutely no trouble enduring the momentary unpleasantness that comes from saying no. As I realized this, I resolved to get a lot better at my own ability to say no."

Buffet also discussed the importance of doing what you love, Spier told CNBC at the time. The billionaire first pointed out that Cecil Williams (the founder of the Glide Foundation) does what he loves by taking care of the less fortunate. Buffett then added that he also he loves what he's doing as the CEO of Berkshire Hathaway.

In fact, Buffett, who is worth $86.3 billion, loves his job so much that he'd be happy doing it for much less. "Certainly with $100,000 a year, I could be very happy," the billionaire told PBS Newshour last year.

He urges young people to find jobs that they love in much the same way. "When you go out in the world, look for the job you would take if you didn't need the money," Buffett told 40,000 attendees at the Berkshire Hathaway 2017 Annual Shareholders Meeting. "You really want to think about, what will make you feel good, when you get older, about your life, and you at least generally want to keep going in that direction."

Spier noted that the billionaire's genuine love for his job was evident at their lunch, adding that it "came across in spades."

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