The cost of drinks will vary greatly. Beer may be as low as $3.00 and premium martini type drinks may be as high as $10 to $12. Wine by the bottle can range from $15 to $XXX.
The suggestions you have received are very good ones. Drinks of the day are a good way to keep your totals down. Beer and wine, by the glass, will usually be in the $3 - $5.00 range.
All mainstream cruise lines charge for alcoholic drinks. Only the luxury lines include most alcohol with your cruise fare. The mainstream lines are: Carnival, Holland America, Princess, Celebrity, Costa, NCL, Royal Caribbean, etc. The luxury lines are the ones that Marc listed, except Windstar (they do charge and they have smaller cabins but beautiful ships). The luxury lines usually have a higher cost per passenger for the lowest category cabin even if you do not consume alcohol. Then again the lowest category cabin isn't a 142 sq. ft.