It’s almost impossible for a modern President to reach the White House directly from the lower economic classes because Americans expect their presidents to be successful achievers. Joe the Plumber cannot be elected president. And that’s a good thing, even if you’re talking about a generic Joe and not the ridiculous character out of the 2008 election.
Most Americans also have the ridiculous idea that political salaries are generally high. The OP talks about a “6 figure bank account” but that’s not wealth in any way. Most middle-class households of the ages of presidential candidates have net worths in the 6 figures. It’s true that the salary for a representative is higher than the median, but you can’t compare the $174,000 they make with the tens of millions a CEO makes, even though the positions are equal in importance. A 6-figure salary gets you into the top 20%, which is nice but not rich.
Both the Obamas therefore had nice but hardly extravagant salaries before office. However, Obama made most of his money from sales of his books. That’s the way most politicians make money in the modern era. Not from graft, as the OP seems to imply. No president these days is likely to make it to office if the public sees them as having benefited illicitly, even if technically legal.
If you go backward through the 20th century, most presidents were career government employees and were not rich by almost anyone’s standards.
Clinton’s salary as governor of Arkansas was something like $35,000, small even by the OP’s standards. Hillary’s law income was needed. Carter ran a successful peanut farm, but he entered politics in his 30s. Nixon also entered politics in his 30s after WWII. He never made any real money until after the Vice Presidency. Eisenhower never made real money until after WWII, either. A career military man doesn’t. Truman shouldn’t count, because he never had a chance of being elected on his own.
Coolidge never did anything other than politics and never had much money, but he shouldn’t count either because he’s also an accidental president. (Ford didn’t even get elected, which is why I left him out). Harding was a successful newspaper publisher but nowhere near rich. Wilson was a professor and university president, both low-paying positions in those days. Taft was another career politician.
Three had made real money from their own efforts. Reagan was a Hollywood star and pitchman for various groups. Johnson made millions from owning essentially a monopoly over the television franchise in Austin. Hoover was a self-made millionaire, having graduated from the first class at Stanford University and building up an engineering firm of world renown.
The rest, the two Bushes, the two Roosevelts, and Kennedy, came from rich families. Kennedy never had a real job, being a career politician. In fact, all of them were essentially career politicians, except Bush 2. He made money from business, although his businesses didn’t.
You can’t argue that only rich politicians get elected president. You can’t argue that most presidents aren’t self-made. You can’t argue that most presidents come from anything other than lower-class or middle-class families. You can’t argue that most presidents get their money from anything but totally legitimate careers.
Yes, some rich people do become president. It would be fantastic is that weren’t true. You can argue that Joseph Kennedy’s money is tainted because of his rum-running during Prohibition, although Daniel Okrent’s book Last Call: The Rise and Fall of Prohibition takes pains to dispel that myth. Johnson’s television monopoly is certainly suspicious. And that’s it. Nobody else’s money is a problem, even in hindsight.
Presidents don’t get to be president by not being ruthless. But they don’t get there by buying their way in. Even the rich ones had to earn their way step by successful step.