I was on a Carnival cruise a few weeks ago and lived on beer buckets. To be quite honest, I don't remember what they cost, but it wasn't expensive. You get 4 beers per bucket but you can't mix beers. They all have to be the same brand. I had no problems taking my bucket between sun decks, back to my room, or back to the hot tub.
We were on the Conquest. A bucket was 11.50, plus 1.73 gratuity, for a total of 13.23. All he bought was buckets. The room steward always made sue he had plenty of ice. But having a fridge in the room helped.