Buffett's company also boosted bets in Goldman Sachs Group Inc.
Buffett also said investors are better off owning a basket of stocks than long-term bonds as a strong US economy bolsters corporate profits, despite higher costs from tariffs.
"That doesn't mean they're going to go up or down tomorrow, next week or next year, but over time, a bunch of businesses that are earning high returns on capital are going to beat a bond that's fixed at roughly 3% for 30 years", he added.
A buy-back policy announced on 17 July gave Buffett, who has gone 2-1/2 years since a major acquisition, a new way to deploy Berkshire's $111.1 billion of cash and equivalents.
And if you have a stock "trading like insane", minutes after you misspeak "you say I misspoke when I said 'funding secured, ' I meant to say I really think I can get funding, something of the sort", Buffett stated.
Berkshire's old policy forbade buybacks unless the price exceeded 1.2 times book value per share.
According to its last regulatory filing, Buffett's firm had increased its stake in Apple to 252 million shares in the second quarter.
Buffett's Berkshire Hathaway has added to its Apple holdings recently, and Buffett told CNBC also on Thursday he had bought "just a little" more of Apple stock. For customers, "the iPhone is enormously underpriced" compared with the utility it offers, he said.
At the restaurant, Buffett held court for hours, over a meal that typically includes his signature Cherry Coke and a $59 Colorado rib eye steak.
The lunch auction raises money for the Glide Foundation that helps the homeless in San Francisco.