I drink bottled water at home, but honestly, when we were on the Grand, I used the tap water on the ship. I added it to the ice bucket and had ice cold water all the time, but in response to being cheap - NO WAY! Tacky? NO WAY!
They charge way to much for bottle water. Bring what you can but try the ships water. Of course, it is a taste issue, some like it some hate it.