I am reasonably sure that the last times I traveled from JER (I don't think I ever brought DF to JER), the best value Duty Free offer were the 600 cigarette packs (3 Cartons), at least for my brand.

And I was always wondering why they were allowed to sell them, as I don't believe there's a flight from JER to anywhere that would allow you to bring 600 cigarettes from outside the EU.

So in a way, they're promoting illegal activities, as are many duty frees around the world that are happy to sell you "multi packs" of cigarettes or offer "Buy X Liters of booze (beyond the limit) and get a free [enter random promotional item here]"

Having said that, I always bought exactly this pack, as it was the best value (like 3 for 2). Of course I always had two friends with me who each carried one carton...