Being ex-president can be lucrative gig

"I think the American people think American politics is all about money," Thurber said. "And this certainly doesn't change their view."

In 1989, right after President Ronald Reagan left the White House, he was lambasted for accepting $2 million for two speeches in Japan, then an economic foe of the United States.

Not all presidents have gotten rich after leaving office.

Harry Truman couldn't afford to answer the copious mail he received or respond to requests for appearances. This prompted Congress to adopt pensions and benefits for former presidents in the 1950s so they weren't forced into activities deemed unsuitable for a former head of state.

Some presidents come into office already very rich. If elected, Republican presidential candidate Mitt Romney would fall into that category. With a net worth of about $200 million, he would be the third-richest president in history.

Adjusting for inflation, Thomas Jefferson and George Washington were the richest people to become president. (Incidentally, the pay they made in office was, for that time, nothing to sneeze at: $25,000).

Washington's wealth in present-day terms has been estimated at more than a half-billion dollars.