Gas Prices

I just don't get it. Gas prices are ridiculous, in more ways than one. For one, it amazes me how quickly the prices rise-when the gas in the tanks is exactly the same. They didn't buy new gas at a higher price and put it in, it's the same lower price gas. Then there's the discrepancy in prices depending on location. I know gas prices are higher in some states due to taxes. But how can they explain the discrepancy between cities? Even nearby cities. Major cities an hour and a half both east and west are less expensive than here. However, what really amazes me is the difference in prices right here. Near me gas ranges in price from $3.91 (it was $3.92 when I left the house, a penny less when I returned) to $4.05. Yet, I went to the doctor and near there gas was $3.73! That's not just pennies! That's a major difference. How can they explain that?!? And why can't the lower prices be located closer to me?!?