Topeka has typically had the lowest in the state over the last couple of years. Usually the lowest places are just west of downtown and just north of the river. Although now the the Topeka Blvd bridge is back up, its not as common. Those stations up there had to bring traffic in somehow over the last couple years.
As of this moment, Topeka has the 15 lowest prices in the state, ranging from $3.17-$3.25
The highest is in Williamsburg at $3.89. That station is usually at or near the top of the list. Manhattan has 4 of the top 15, with Wamego and St Marys chipping in one each.