If I remember correctly... the cups cost arount $7.00 and the unlimited soda was apprx. 20.00 per person for our cruise which sailed on Monday and returned on friday.
We loved it, after a while you didn't have to show your soda card, because the bartender knew you. It was great.
We also bought the bottle holders which we used for our red carnival cups. It was great we just threw it around our necks and away we went.
I think the cup/bottle holders were about the same price as the red cups.
We definately got our money's worth. By the way, you can go to any bar and fill up on juice too.