Billionaire investor Mario Gabelli has scored a 6,200% gain on Warren Buffett's Berkshire Hathaway

• Mario Gabelli bought $1.3 million of Berkshire Hathaway stock in the 1980s.
• The billionaire investor's stake in Warren Buffett's company is now worth $83 million.
• Gabelli paid an average of $6,000 for shares now worth over $370,000 each.
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Billionaire investor Mario Gabelli has been richly rewarded for his faith in Warren Buffett's Berkshire Hathaway.

The Gamco Investors CEO snapped up more than 200 of Berkshire's "A" shares for two of his funds in the late 1980s, he told CNBC this week. Gabelli paid an average of $6,000 for the shares, which now change hands at north of $370,000 each.

Overall, Gabelli paid about $1.3 million for Berkshire stock worth $83 million as of Tuesday's close - an astounding 6,200% gain.

The Gabelli Asset Fund and Gabelli Equity Trust owned a total of 218 Berkshire "A" shares worth $76 million as of December 31, SEC filings show. Berkshire's stock price has climbed about 9% to record levels since then, boosting the value of Gabelli's stake to fresh highs.

Gabelli's outsized gain required not only the foresight to back Buffett's conglomerate more than 30 years ago, but the discipline not to cash out his stake.

Those traits aren't too surprising, given Gabelli sums up his investing approach on Twitter as "Graham & Dodd + Buffett = Gabelli." In other words, he sees himself as a mix of Buffett and two of the Berkshire's chief's mentors, Benjamin Graham and David Dodd.