"Due to Mr. Buffett's and Mr. Munger's desire that their compensation remain unchanged, the Committee has not proposed an increase in Mr. Buffett's or Mr. Munger's compensation," Berkshire Hathaway said in a securities filing Friday.

In a world where Wall Street firms give lavish compensation to their managers even as many underperform the stock market, the Oracle of Omaha gets paid just $100,000 in salary per year.

The company said Buffett's compensation hasn't changed in more than 25 years. Meanwhile, Buffett manages Berkshire's $170 billion stock portfolio and guided the company's market value to a 20.9 percent annual return from 1965 to 2017 versus the S&P 500's 9.9 percent gain.

Buffett's frugality for Berkshire does not end with his salary. The filing also reveals he gave $50,000 last year to the company for the reimbursement of personal expenses such as postage and phone calls.

"Mr. Buffett will on occasion utilize Berkshire personnel and/or have Berkshire pay for minor items such as postage or phone calls that are personal. Mr. Buffett reimburses Berkshire for these costs by making an annual payment to Berkshire in an amount that is equal to or greater than the costs that Berkshire has incurred on his behalf. During 2017, Mr. Buffett reimbursed Berkshire $50,000."

To be sure, Buffett doesn't need the money. He has an estimated net worth of $87.6 billion primarily from his 38 percent stake in Berkshire Hathaway Class A shares, good for third richest person in the world, according to Forbes.

But the investor sure goes out of his way to underpay himself for shareholders' benefit.