Warren Buffett is paying a hefty price for the biggest bet of his career as his Berkshire Hathaway Inc. has agreed to buy Precision Castparts Corp., valuing the maker of aerospace and other parts at $32.3 billion. The purchase is Berkshire's largest, and it accelerates its transformation from a company largely dependent on insurance businesses into one resembling the broader U.S. economy, including a railroad, several industrial companies, utilities, a car dealership and consumer goods businesses.