What I don't get is the wide varation in prices from one city to another and I would assume it's the same gas supplier for each city.

Here's a quick recap of a story I heard from a reliable source about raising gas prices.

A guy that works at a well established place that sells gas received a call to raise their prices and see if everyone would follow them. And of course after they raised their prices everyone else raised theirs also.

Also Exxon Mobile posted the largest one year profit for a company in history.

Sounds like price gouging to me