Gas prices top \$2 a gallon in state It's back: \$2 gasoline. After sliding steadily from late June through the Labor Day weekend, the average price for a gallon of self-serve unleaded gasoline in Massachusetts was back up to \$2.01 yesterday, according to the most recent survey by the American Automobile Association. The nationwide average also crossed over the \$2 threshold between Sunday and yesterday, AAA said.