There was one guy selling gas at this small station in Sausalito, California. For some reason he started jacking up his prices and many tourist and some oddball locals still paid for it even though the Shell station a mile away was much cheaper. When he got complaints he raised the prices even higher. It was really weird.
Why Sausalito gas station charges nearly $8 a gallon
www.sfgate.com
Other than that, I've seen some prices that were extremely high in remote locations. I was at Sequoia and Kings Canyon National Parks where the Chevron stations that used to be public were converted for only use by Park Service and concession use. The only gas stations in the area were privately owned and on leased Forest Service land - the Hume Lake Christian Camp, Stoney Creek Lodge, and Kings Canyon Lodge. The last one was really different. They had a 5 gallon minimum and used an old fashioned gravity feed system. They were rusty when I saw them, but I saw that they had repainted them. And they had a county ag weights and measures sticker just like a modern gas pump. The price was maybe $2/gallon more than gas in Fresno.