The world's second richest person, Warren Buffett's company Berkshire Hathaway, on Tuesday became $400 million richer after Apple stock hit an all-time high. Berkshire holds 15.22 million shares of Apple which were worth $1.6 billion in August last year. When Apple shares hit record high, Apple's market value touched $669 billion, valuing Berkshire's stake $400 million more at $2.04 billion.