Including the 15% automatic gratuity, a can of soda costs $1.73. On our last cruise we got the soda card for our son and it was $32.20 (again including the tip). An adult card is more expensive - about equal to the price for 25 cans of soda. The kid's card equals 18 cans in cost. The soda card does not get you a can of soda. It gets you a glass filled from the bar fountain - about 8 ounces or less per serving.