Well, there is the cost of the cup. Looking at the pricing, it appears they priced the physical mug at $5.99 and then $3 per day for soda. $5.99 is obviously not the true cost to produce but not horrible when compared with other souvenir prices. Personally I've never seen the value in the mugs. Have no desire to carry around a sticky, undersized plastic tumbler wherever I go. And like another poster said, I could drink the entire contents just on my walk from the refill station to hotel room. It's just one more reason we rent a car and make our own grocery trip. The $18 x 4 we'd have to pay for mugs would more than cover the cost of a single day car rental. And with it we can buy our own choice of beverages plus other snacks and necessities.