OMAHA, Neb. (AP) — The cost to dine with investor Warren Buffett has apparently spiked in value, with one deep-pocketed bidder forking over nearly $3.5 million.

The annual charity auction for a private lunch with the Nebraska billionaire closed Friday night following a flurry of activity in the final hours. In the end, the highest bid was $3,456,789, topping last year's $2.6 million winner.

It wasn't immediately clear who offered up the winning bid.

The auction benefits the Glide Foundation, which helps the homeless in San Francisco. Buffett has raised more than $11.5 million for the organization in 13 past auctions.

The billionaire became one of the world's richest men while building Berkshire Hathaway into a conglomerate. But he says most of the questions he gets at the lunches aren't about investing.