You can not tell me ALL the booze they sell in Europe or Asia on a 4 or 6 month tour has come all the way from the USA,,,it dont, think about it, neither does the food or anything else used on that ship
The stocking of stores for the ship is not so simple. Often what you're seeing being loaded onto the ship are goods actually bought elsewhere and shipped to the port ... for restocking purposes.
It's not that they don't also buy local products, but there's many things that are calculated into their buying decisions. Not the least of which is currency values.
For some time the Euro has been quite strong against the value of the U.S. dollar.... and in some cases (when stocking entire fleets) the currency exchange can be significant enough to buy elsewhere and ship good to the ships in various ports of call.
You can't equate the costs to the same as it is with you going to the local liquor store or market.