Berkshire Hathaway is a special case because it was a failing company. When Buffett bought it, it was a textile company and he's transformed it into a holding company for insurance and monopolistic business like Heinz and Coca Cola.
From wiki on Berkshire Hathaway
In 1962, Warren Buffett began buying stock in Berkshire Hathaway after noticing a pattern in the price direction of its stock whenever the company closed a mill. Eventually, Buffett acknowledged that the textile business was waning and the company's financial situation was not going to improve. In 1964, Stanton made an oral tender offer of $111⁄2 per share for the company to buy back Buffett's shares. Buffett agreed to the deal. A few weeks later, Warren Buffett received the tender offer in writing, but the tender offer was for only $113⁄8. Buffett later admitted that this lower, undercutting offer made him angry. Instead of selling at the slightly lower price, Buffett decided to buy more of the stock to take control of the company and fire Stanton (which he did). However, this put Buffett in a situation where he was now majority owner of a textile business that was failing.
Buffett initially maintained Berkshire's core business of textiles, but by 1967, he was expanding into the insurance industry and other investments. Berkshire first ventured into the insurance business with the purchase of National Indemnity Company. In the late 1970s, Berkshire acquired an equity stake in the Government Employees Insurance Company (GEICO), which forms the core of its insurance operations today (and is a major source of capital for Berkshire Hathaway's other investments). In 1985, the last textile operations (Hathaway's historic core) were shut down.
In 2010, Buffett claimed that purchasing Berkshire Hathaway was the biggest investment mistake he had ever made, and claimed that it had denied him compounded investment returns of about $200 billion over the subsequent 45 years. Buffett claimed that had he invested that money directly in insurance businesses instead of buying out Berkshire Hathaway (due to what he perceived as a slight by an individual), those investments would have paid off several hundredfold.