Ben Bernanke earned more in 40 minutes on Tuesday than he made all of last year as head of the U.S. Federal Reserve. Bernanke was paid at least $250,000 for his first public speaking engagement, in Abu Dhabi, since stepping down in January, according to sources familiar with the matter. That compares to his 2013 paycheck of $199,700, and the appearance was only the first of three around the world this week. Bernanke's public post-Fed debut was a departure from the private audiences that his predecessor Alan Greenspan addressed shortly after he handed over the central bank's reins in 2006. In his remarks, Bernanke recounted the Fed's response to the 2007-2009 financial crisis, an issue he is exploring for a book he plans to shop around to publishers. (Read more: Bernankesays Fed could have done more during crisis) In hitting the speaking circuit, Bernanke is following a well-trod path of top public servants cashing in on the demand for the insights they can offer. In the case of a one-time Fed chairman, those insights could potentially be market-moving. And given that his successor, Janet Yellen, has vowed to stay the course he set, investors could view him as a weather vane for the world's most powerful central bank.

"He will obviously be enjoying the fruits of the free market," said Jan Baran, a partner and head of the election law and government ethics group at Washington law firm Wiley Rein LLP. "He will personally experience supply and demand." Lawyers and agents say Bernanke, 60, should be able to command around $250,000 per speech for a while to come. The paycheck "sounds reasonable to me," said one speaking-circuit agent who did not want to be named. Bernanke could have a "very long shelf life," he added. While the fee launches him into the upper echelons of sought-after speakers, it leaves him well short of former President Bill Clinton—the gold standard of Americans turning charisma into cash—who has, by some estimates, earned two or even three times that much for some appearances in recent years. (Read more: Bernankecracks wise: The best QE joke ever!) "He's free to offer his own views either historical or forward-looking," said Baran, when asked about the ethics of Bernanke cashing in on his eight years as Fed chairman. "Nothing sounds illegal or unethical and in fact it sounds fairly routine."