The most expensive publicly traded stock of all time is Warren Buffett’s Berkshire Hathaway (BRK.A), which is trading at $305,500 per share, as of Oct. 23, 2018). Berkshire hit an all-time high on Oct. 9, 2018, at $335,900. Thanks to spectacular shareholder gains and the idiosyncrasies of its founder, this share value is unlikely to be matched by anything other than continued gains in Berkshire’s share price.  

Berkshire Hathaway share price

The next company behind Berkshire, in terms of stock price, is Seaboard Corporation (SEB), which trades at $3,780 per share. Then there's NVR (NVR) at $2,198, Booking Holdings (BKNG) at $1,818 and Amazon.com (AMZN) at $1,734.  

The reason why certain stocks are priced so high is usually due to the company having never completed a stock split.

Top Companies by Market Cap

By market capitalization, Apple (AAPL) is the biggest company at $1.08 trillion, followed by Amazon.com (AMZN) at $876 billion, Microsoft (MSFT) at $839.4 billion, Google (GOOGL) at $764.6 billion and Berkshire Hathaway at $508.7 billion.

Back in 2000, Chinese energy giant PetroChina (PTR) reached an estimated market value of around $1 trillion during its IPO. However, this valuation included shares not publicly traded in the total share count calculation, and the valuation didn't stick. As of Oct. 2018, PTR's market capitalization stood at $215.2 billion. 

Top Companies by Revenue 

In terms of the biggest global companies by revenue, Walmart (WMT) comes in as number one -- according to Fortune. Walmart's revenues were $500.3 million last year. Behind Walmart is State Grid with $348.9 million in revenues, then Sinopec Group with $327 million and China National Petroleum at $326 million. Royal Dutch Shell ranks fifth with $312 billion in annual revenues, and the sixth and seventh spots are covered by car giants. Toyota Motor and Volkswagen generate $265 billion and $260 billion in yearly revenues, respectively. 

Based on just U.S.-headquartered companies, Walmart still has the top spot, while ExxonMobil (XOM) comes in second with $244.4 million a year in revenues. Berkshire Hathaway ranks third with $242 million and fourth is Apple with $229 million. Health care companies take up the fifth through seventh spots: UnitedHealth Group, McKesson and CVS, generating $201.2 million, $198.5 million and $184.8 million, respectively. 

Top Private Companies

In terms of private companies, Forbes ranks Minnesota-based Cargill as the largest private U.S. company with $114.7 billion in annual revenues. The company has 155,000 employees. Second is Koch Industries with $110 billion in revenues and 120,000 employees. Ranking third is the grocery chain Albertsons, with $59.9 billion in annual revenue and 275,000 employees. 

The fourth and fifth largest private companies are accounting giants Deloitte and PricewaterhouseCoopers, which generate $43.2 billion and $41.3 billion, respectively. Each employs over 236,000 employees.  

The Bottom Line

On a pure market value measure, Apple is the most valuable company of all time. Although Amazon did briefly hit the $1 trillion market cap mark in Sept. 2018. It is certainly possible another company’s market cap will exceed Apple's, and maybe -- though less likely -- another company will surpass Berkshire Hathaway as the highest priced single stock.