Former president George W. Bush is earning big bucks making speeches, with a fee of between $100,000 and $150,000 per appearance.

According to iWatch News, Bush has raked in about $15 million on a speaking circuit since vacating the Oval Office, while maintaining a relatively low public profile.

Bush’s spokesman David Sherzer told iWatch that Bush has made about 140 paid speeches both in the US and abroad since his presidential term expired – almost all of which are closed to the press.

iWatch reported that when Bush declined an offer from President Barack Obama to appear at Ground Zero in New York following the killing of Osama bin Laden was killed, he was actually preparing to make three private speeches during that week.

Bush’s predecessor, Bill Clinton, has also made a mint making speeches around the world.

According to CNN, Clinton amassed $65 million in speaking fees from 2001 to 2009. In 2009 alone, he took home $7.5 million from 36 speeches.

Last year Clinton addressed his speaking fees.

I never had any money until I got out of the White House, you know, but I've done reasonably well since then, Clinton said at a forum in South Africa.

Scholars and presidential experts are troubled by the practice of ex-chief executives making money this way.

“I find it puzzling,” UCLA history professor Robert Dallek told iWatch. “[Bush] says he wants to keep a low profile. What is he doing except enriching himself? It sounds like it’s self-serving. It’s following the good old American adage to make as much as you can.”

Similarly, Julian Zelizer, Professor of History and Public Affairs at Princeton University told iWatch: “It’s one thing to stay out of the public realm, which George Bush has said he wants to do. But then he goes on the speaking circuit and makes enormous amounts of money giving lectures mostly to corporate groups and other select audiences. Some Americans can find this distasteful.”

Zelizer further stated: “We’re in an era where there are countless fears about money and politics. I think former presidents have to be careful about what they’re doing with their speeches. For some people it’s another version of the revolving door between Capitol Hill and K Street.”