iceland taxes the heck out of it, and there are only a few stores where you can buy
I paid $20 apiece for shots at a bar in Reykjavik. I paid (IIRC) $5 for a bottle at the airport.
(The bars are especially expensive. I'm told that all the Icelanders pre-game before going out drinking. If you plan to drink while in Iceland, pick it up on your way in.)