Warren Buffett, billionaire

Warren Buffett, billionaire, leader of titanic conglomerate Berkshire Hathaway, and "Oracle of Omaha," is undoubtedly one of the very most famous investors alive today. He commands such tremendous respect among fellow investors that his suggestion of a possible investment opportunity can send stock prices through the roof. There is good reason why many investors follow Buffett's every word when it comes to financial matters: over the course of his decades-long career, Buffett has built Berkshire Hathaway (BRK-A) from a small textile manufacturing outfit into one of the largest and most powerful companies in the world. Buffett tends to buy stocks of companies he feels are undervalued and hold his positions for a long time, and that is the case with his position in Bank of New York Mellon Corp. (BK). Buffett first bought this stock in late 2010. Here's how much money you would have earned on your investment if you had bought BK stock when Buffett did.

Buffett Bought BK in Q3 2010
Buffett first disclosed a Berkshire Hathaway stake in BK in his company's 13-F filing for Q3 of 2010. That means that he bought his first shares sometime between the beginning of July and the end of September of that year. By the end of the quarter, according to a report by Forbes, Buffett had accumulated about 1.9 million shares of the stock. Given the way that 13-F reports work, it is unclear whether Buffett bought these shares all in one go at some point in that three-month period, or if perhaps he made several smaller purchases in that time, the sum total of which was nearly 2 million shares. In any case, according to data provided by Google, BK shares hovered between $25 and $27 each during the window in which Buffett made his first purchase. The stock sold for $25.73 per share on July 16, 2010, and for the purposes of our estimate, we will consider that to be the price that Buffett paid.

From $25.73 to $49.55
Since Buffett bought BK for the first time in 2010, the price of the stock has nearly doubled. As of this writing, the stock is trading for $49.55 per share. That means that if you had purchased, say, 100 shares of BK stock (for a total of $2,573) in 2010, those 100 shares would now be worth $4,955. This constitutes a gain of about 92%.

Of course, Buffett did not leave his investment in BK at the initial 2 million shares. In fact, as of the end of Q1 of 2017, Berkshire Hathaway has more than 33 million shares of the bank's stock. This accounts for more than 3% of all outstanding BK shares, and it also means that Buffett's investment is currently worth about $1.65 billion.

Reference: http://www.investopedia.com/news/how-rich-followed-warren-buffett-bank-new-york-mellon-brka-bk-berkshire-hathaway/