Frugal billionaire Mark Zuckerberg continues to enjoy his budget holiday in Hawaii with his wife Priscilla Chan, while it has been revealed he is even richer than previously thought.

Mark Zuckerberg, 28, gained $2.3 billion from selling 60 million stock options just before Facebook’s initial public offering last year.

Facebook’s CEO and his Harvard-educated doctor wife are also rumored to be on the lookout for real estate in Hawaii.

Despite his latest windfall, sport-shorts wearing Mark Zuckerberg remains focused on the simple things in life. Rather than indulging in lavish dinners and extravagant outings, he has been spotted eating burgers and surfing in recent days.

Mark Zuckerberg isn’t the first frugal billionaire, Warren Buffet is another who would prefer to keep his wealth in the bank rather than spend it on extravagant purchases. He famously still lives in the same modest home he bought in 1958 for $31,500.

Facebook’s CEO has another reason to keep his vacation cheap and cheerful. According to regulatory documents filed Friday, he has also been saddled with a massive $1.1 billion tax bill. Money he raised by selling 30.2 million Facebook shares for $38 apiece in the IPO.

Frugal billionaire Mark Zuckerberg continues to enjoy his budget holiday in Hawaii with his wife Priscilla Chan, while it has been revealed he is even richer than previously thought

Facebook’s stock hasn’t closed above $38 since the IPO was completed last May. The shares gained 71 cents Friday to close at $26.85.

The 29% decline from Facebook’s IPO price has cost Zuckerberg nearly $7 billion on paper, based on the 609.5 million shares of company stock that he owned as of March 31, according to the regulatory filing. His current stake is still worth $16.4 billion.

Mark Zuckerberg, who started Facebook in his Harvard University dorm room in 2004, has indicated he has no immediate plans to sell more stock.

The proxy statement filed to announce Facebook’s June 11 shareholder meeting is the first time that the magnitude of Mark Zuckerberg’s stock option gain had been quantified.

The proxy also revealed that Mark Zuckerberg’s pay package last year rose 16% because of increased personal usage of jets chartered by the company as part of his security program.

Mark Zuckerberg’s compensation last year totaled nearly $2 million, up from $1.7 million last year. Of those amounts, $1.2 million covered the costs of his personal air travel last year, up from $692,679 in 2011.

If not for the spike in travel costs, Mark Zuckerberg’s pay would have declined by 17%. His salary and bonus totaled $769,306 last year versus $928,833 in 2011.

But despite being worth $13.3billion, Mark Zuckerberg enjoys life’s simple pleasures. Earlier this week he and his wife were spotted chatting with friends at picnic tables while snacking on Kauai’s famous Bubba burgers and smoothies.

The couple, who are notoriously down-to-earth, sported casual wear and Mark wore his now-famous sandals, which are parodied by Jesse Eisenberg in the film about Facebook, The Social Network.