The price of oil is a factor of so many different things, much of it is pure speculation on the political relations in foreign countries, as well as the speculation of investors which includes any stock holders. It's not just drilling and selling, it's speculation on how much it is worth. While it's true that ExxonMobil drills, they are the 14th in the production of oil and obviously do not have the power to sell oil at whatever price they would like. The CEO of the company has been saying that the price is too high, and that it's an artificial bubble. I believe him.
Also here's a link on profit margin's.
Oil Profit Margins vs. Other Industries « The Everyday Economist