Fuel stations taking advantage?

A109 Light Utility Helicopter flight with mayor Gisborne City from the air in November 2023.

I read in The Gisborne Herald that the tax on fuel will be going back to the full rate at the end of June this year.
Well, three weeks ago when my wife and I were about to drive to Hamilton Hospital, we filled the car up with 91 and it was $2.35 a litre — which we were happy with. After spending 16 days in Hamilton we returned home to find that the price of 91 was at $2.50 a litre. 
When in Hamilton, the average price per litre was between $2.16 and $2.40 — so are fuel stations price fixing or what?

I’M CONFUSED