Warren Buffett's Berkshire Hathaway saw the value of its Apple stock tumble as much as $19 billion in two days.br On Thursday, Apple's stock price dropped 8.br On Friday, Apple dropped as much as 7.br That cut the value of Berkshire's roughly 981 million shares in the tech titan to below $110 billion.br Berkshire has still more than tripled the value of its Apple investment, as it spent about $35 billion to build the 5.7 stake.br Berkshire Hathaway's Apple stake is still worth more than the market capitalization of Citigroup or Starbucks.