Although I may be wrong about oil profits being excessively high.

According to ConocoPhillips, the profit margins are not that large, percentage-wise, as compared to other U.S. industries.

Although when you're talking about an industry that operates in the tens or hundreds of billions, even a slight percentage increase works out to an enormous amount of money.

The same link above also argues that there is significant federal regulation of the oil industry, going back to the early 70's.