Ames is among three cities with the most expensive gasoline in the state. Triple A says local price averages match Des Moines and Dubuque at $2.89 a gallon. Overall, the cost of a gallon of regular gas statewide is almost a nickel higher than a week ago at $2.84. The national average is $2.96. Iowa's lowest average gas price is in Sioux City at $2.76 for regular unleaded.