Find Your Cruise
You will probably get some astute answers but the cheapest thing to do is.... Not to buy any, now that's cheap... Neil.
The cheapest is Spain (about 25€). In the duty free shop in Palma de Mayorca 21€ for cruises outside EU. Happy shopping!
Spain,Ship,Portugal,France In this order. The ship does not carry all brands so it depends on what brand you require as well.