New filings show, as Buffett's Berkshire Hathaway bought another 900,000 shares of Phillips 66. In total, during the six days, Berkshire has bought just over 5 million shares of the company at an average price of $76.58 per share. That's almost $400 million worth, a small, but growing, percentage of Berkshire's total stake that's now worth more than $5 billion.