Well, I just got off the Crown Princess and we paid $31 for a soda pass and that included a insulated metal cup with cover.
There is a charge for ice cream, like around $3 but I didn't like it at all. It doesn't taste like your usual soft serve. I had a few bites and threw it out. Though, flavored sorbets and ice creams offered in the dining rooms for free as dessert are very good. One night I had blueberry sorbet and it was great. Real, fresh blueberries inside.
On the second formal night, there were lobster tails offered in all the dining rooms so if you want to hold off until then, it's worth it. I know the restaurant that offered lobster regularly had a cover charge to eat there then another charge for lobster. Not worth it.