In a 2010 letter to investors, he noted that Pure Heart Value Investment Fund's yearly return on investment was 0.5 percent, and Pure Heart Natural Selection Fund's yearly return was minus 8 percent.

All for charity

Buffett's power lunch, traditionally held in a high-end New York steakhouse called Smith & Wollensky — which itself donates $10,000 to the cause for the pleasure of hosting the event annually — is legendary in the world of finance. When it started in 2000, interested parties simply had to fork out a paltry $25,000 for the food and the table talk. Today the price has risen more than 138-fold.

The restaurant donates $10,000 to the charity Glide for the pleasure of hosting the event annually. Warren Buffett and Wang Chuanfu, CEO of the auto and battery maker BYD, presenting a key to the millionth person to own a BYD car on Sept 27, 2010. Provided to China Daily

Given the fragile state of the US economic recovery — unemployment rose to 8.2 percent in May — and Buffett's announcement that he had been diagnosed with prostate cancer, the scale of this year's winning bid astonished many observers and bucked a run of low bids in the five-day auction process.

Observers adopted a cautious wait-and-see attitude as the bids rose slowly during the first four days of the five-day event. The last bid on June 7, the penultimate day of the auction, was just $410,000.

However, the proceedings saw a dramatic change on the final day as the amounts offered surged in the last 15 minutes of bidding, from $1,234,467 to a record-breaking $3,456,689 when proceedings wrapped up at 7:30 pm on June 8. Thus far, the only information available about the winner is their eBay ID, s***7 and their nationality is unknown.

Duan Yongping, the founder of both Subor Electronics Industry Corp and BBK Electronics Group, submitted a winning bid of $620,100 in 2006 and became the first Chinese to join the charity lunch.

In a video interview with the Internet portal Netease conducted soon after the meal, Duan said he did not think it was accurate to say that he had spent $620,100 on the meal.

"Actually no one paid for the lunch, except maybe Mr. Buffett himself because he tipped. It was more of a charity activity. He was helping the Glide Foundation (a nonprofit organization that provides aid for the homeless in San Francisco). We just had the chance to sit down and chat. It wasn't a business deal, so you can't say it was a loss or a gain," said Duan, an active philanthropist in China and co-founder of a nonprofit charity called Enlight in the US.

"And you cannot simply say that it was or wasn't expensive. I once did a rough calculation of Mr. Buffett's average hourly earnings and the number was around $3 million. My $620,100 secured lunch with him for more than three hours," said Duan.

Admitting that the lunch turned out to be very rewarding, even though he had not had any specific expectations, Duan said that afterwards his investment strategy remained almost unchanged.