Yet Mr Buffett has built a devoted following, as demonstrated by the crowd of 35,000 people at his recent Berkshire Hathaway shareholders meeting, and he offers only one lunch per year.

The online bidding begins at US$25,000 on Sunday in a charity auction that benefits the Glide Foundation, which provides social services to the poor and homeless in San Francisco. The bids will likely escalate significantly before the auction closes on Friday evening at 2200 EDT (1000 Saturday Singapore time ).

Glide's founder, Reverend Cecil Williams, said last year's big bid arrived just in time because demand for Glide's programs jumped roughly 20 per cent in the past year with the recession. Glide relies on donations for most of its US$17 million budget, so Mr Williams is hoping for another big bid.

Mr Buffett's late first wife, Susan, introduced the billionaire investor to Mr Williams and the Glide Foundation. Mr Buffett says he enjoys being able to help Glide with the lunch.

Mr Buffett, who is Berkshire's chairman and chief executive, is primarily known for his investing success. Berkshire owns more than 60 subsidiaries including insurance, furniture, clothing, jewellery and candy companies, restaurants, natural gas and corporate jet firms and has major investments in such companies as Coca-Cola Co and Wells Fargo & Co.

But Mr Buffett is also known for his philanthropy. In 2006, he announced his long-term plan to give away the bulk of his roughly US$36 billion fortune. Most of his shares of Berkshire stock will go to five charitable foundations, with the largest chunk going to the Bill & Melinda Gates Foundation.

Previously, the most expensive charity item ever sold on eBay was a letter from Democratic senators blasting conservative talk show host Rush Limbaugh for using the phrase 'phony soldiers' on his program. The letter signed by 41 senators sold for US$2.1 million on eBay in October 2008. -- AP