I would probably buy a carton of smokes for a buddy if Duty Free really offered a huge savings. In my home state, it doesn't. Miles wouldn't come into play...I'd just do it as a favor for a friend if I lived in one of those seven-bucks-a-pack states.

I always buy single malt at Duty Free. Those prices ARE significantly cheaper than my home state's prices. I just blew through a bottle of Dalwhinnie, which means it is now time for me to take another trip.