Just been on a cruise 2 months ago with Costa in the Med. My wife and I are not heavy drinkers possibly a couple a night each. You do not pay by cash, you receive a kind of credit card that you settle up at the end of the cruise. We ran up a bill of €250 for a week plus the excusions. There is service charges on the drinks, Plus at the end of the trip there was a daily gratuity added. We found that when we asked for water in the restaurant it was costing about €6.50 a bottle, we quickly caught on that if we asked for regular water it was out of the tap and cost nothing.