That's very true, Nick. Also, the funding they get from the criminals they all pardon on their last day in office, the multi-million dollar book deals, the huge presidential pensions, secret service protection, housing allowances, office allowances, the multi-million dollar law-firm partnerships they are offered in order to bring Presidential prestige to law firms, etc.
On the other hand, a President might be "indebted" to some of the constituents who put him in office, so might make some decisions with a bias.
In the end, though, the President's finances have got to be the most scrutinized finances of anyone on the planet today. If any President were 'getting rich' from his official actions, he would be discovered immediately and impeached. Or worse yet, he'd be found out by the opposing party and blackmailed.
These days it is so hard to hide money (especially a lot of money) thanks to the Patriot Act, and SarbOx, too.
Erm, doesn't an ex-president of the US do very well by doing speaking tours at $100,000 per hour? I don't think they have to worry about 'getting' rich as a result of what they have or haven't done during their presidency.