FWIW, from what I've read, our refineries are at capacity and we are not producing enough to be self sufficient.
US refineries have been running at 84 - 85% of capacity in 2008. Practical maximum is about 95%, so they are some way off.
It's certainly true that the US is not refining all the crude it uses, but then again the US doesn't produce the crude. The US is a major oil importer, it makes sense to import finished product, and have the refineries located in third world countries, with third world labour rates.
The reason for high gasoline prices is the high price of oil. Indeed, US gasoline is priced too cheap at the moment.
You get 42 gallons from a barrel (it's actually more complex than that because you also produce diesel, heavy oil, lubricants, plastic feed stock etc). At 42 gallons a barrel, and $100 a barrel, a gallon costs about $2.4, without the costs of refining, transporting and selling, or taxes.