Are you saying there is a charge for coffee when you order it at one of the bars where alcoholic beverages are served?
If that is the case, I'm surprised that they have not charged for it before. When one orders any alcoholic beverage at the bars, there is a charge for it, plus the automatic 15% gratuity. This is served to you by the bar attendant. It's not like you go up to the coffee urn in the buffet and get your own. This is served to you.
Sounds like the coffee costs $1 and the 15 cents is the gratuity. That's cheaper for coffee than at many restaurants on land.