Being overpriced is an understatement. As far as the crew watering down a bottle behind the bar, I've never heard of that or experienced that on the three cruise lines we use, I really doubt if that has ever occurred.
I'm not happy with the variety of and quality of reds (wine) HAL and Princess offer for sale anymore, they used to be much better. Princess sells a bottle on board to me for $33.00 which I can get at COSTCO for a little over $5.00. However, they will let me bring on board all the COSTCO wine I want as long as I pay their $15.00 surcharge for each bottle when I come back on board. Guess that is fair, but I remember the days they let me bring all I wanted on board for free. HAL was the last to discontinue that practice, and now they charge $18.00 for every bottle I bring on board. (Except, two free at the beginning of the voyage.) (On more than a couple voyages we have been on it has been weeks before we ported anywhere that had a decent liquor store on shore, though.)