The most expensive publicly-traded share of stock of all time were the Class A shares of Berkshire Hathaway (BRK.A), Warren Buffet’s conglomerate and holding company as of January 2022. They hit $487,675 per share on Jan 18, 2022. It’s important to remember that this does not mean it is the most valuable company by stock value. The value of a company’s stock, or “market capitalization,” is determined by multiplying the price of its shares by the number of its shares.