Executive one-on-ones are a hot commodity. You can look to Apple CEO Tim Cook's recent offer to share a coffee--and up to one hour of his time--with the highest bidder as an example.

The bidding for a coffee date with Apple's head honcho, originally valued at $50,000, started with a $5,000 offer Wednesday morning on the celebrity fundraising site Charity Buzz and has since climbed to more than $100,000. For a coffee.

But Cook isn't the first entrepreneur to raffle off his highly-coveted time for a good cause. Here are four other high-profile execs bringing new meaning to the phrase "time is money."

Warren Buffett

Every year, the chairman of Berkshire Hathaway auctions off a lunch meeting to raise money for the San Francisco charity organization, Glide, which serves warm meals to the hungry and operates a church in the city's troubled Tenderloin district. Buffett, who was turned on to the charity by his late wife, has raised over $14 million for the organization since 2000.

And Glide hasn't been the only party to benefit from this annual fundraiser. Ted Weschler, a former managing partner for Penninsula Capital Investors, won both the 2010 and 2011 auctions--and later landed a job overseeing Berkshire's investments.

Sir Richard Branson

In December, Sir Richard auctioned off a five-day vacation for two on his private Necker Island during the Necker Cup tennis tournament--another of Branson's creations--which included a dinner with the entrepreneur and tennis players Novak Djokovic and Tommy Haas. Though the winners and final bid from the auction were not disclosed, the Necker Cup raised over $500,000 in a silent auction, which benefited the National Tennis Foundation, Virgin Unite, and other leading ATP player charities.

Elon Musk

Serial entrepreneur Elon Musk of PayPal, Tesla Motors, and SolarCity fame is currently raffling a 10-person tour of his SpaceX Center in Hawthorne, California to benefit the RFK Center for Justice and Human Rights, a global advocacy group. The tour includes an inside look at the "fabrication and assembly of rockets, engines, and spacecraft" and a face-to-face meeting with Musk himself. An anonymous bidder placed an opening bid of $5,000 on Wednesday morning, but the host site Charity Buzz estimates the tour to have a value closer to $25,000.

Michael Bloomberg

The mayor of New York City and founder of the Bloomberg media empire auctioned off a lunch meeting in New York last November to benefit the Humane Society of the United States. It appears that a lunch with the politician didn't quite warrant Buffett's multimillion-dollar pricetag, but Bloomberg still collected an impressive $185,000 for his cause.