I recently sailed on a 7-night Royal Caribbean cruise aboard an Oasis-class ship with my 7-year-old child. I considered buying the drink package beforehand but ultimately decided to pay as I went, thinking I could stay well below the package price.
Some of my purchases were made in the evenings while my child was at the kids' club, while others included ordering two drinks at a time by the pool. I also bought bottled water, coffee, and a couple of milkshakes throughout the trip. I actually skipped specialty coffees most of the time.
As for alcohol, drinks went down surprisingly easily on hot sea days, especially with all the food available onboard. Even after several drinks, I rarely felt intoxicated. In fact, there was only one evening when I actually felt drunk. I am not much of a drinker in everyday life, but vacation tends to be the exception.
By the end of the cruise, my total spending on drinks came to $791.65 USD.
For comparison, the drink package currently offered on my upcoming Carnival cruise would cost $881.92, and that price also includes premium Wi-Fi for the duration of the sailing.
The biggest downside to paying individually was constantly keeping track of my spending, wondering whether I was staying within budget, and occasionally thinking that having the drink package would have eliminated that stress. I am not sure whether I would have consumed more with the package, but the peace of mind alone has value.
For me, paying a bit more for the package may be worth it simply to enjoy the cruise without worrying about every drink purchase.

