ARCO

I bought a AMPM big cup like a thermos with the logo on it I went into a hundred and 8th and Prairie address 10800 South Prairie and the lady tells me it's a dollar 55 there anywhere I go I paid $0.50 to nothing even at this establishment so how does the ice go from $50.to55. Cent it always depends on who's working i can't understand why its a big change