Do all Duty Free shops have the best prices all over the world?

I’m currently planning a trip to Greece. I’ve heard tale of a Grape Whiskey I might like (Raki, I think its called). But i’m debating if I should buy it in stores outside of the Athens Airport or in the Duty Free Shop.

I’m only asking because when I visited Ireland, I was pleasantly surprised when I found out that they carried Fercullen 15 YO Whiskey at a decent discount.

Then when I went to Poland, I found this peppercorn Vodka I really loved. But to my horror, I found out too late that I could have bought 3 whole bottles at the Duty Free Shop than when I bought it at the Warsaw Mall.

Now, i’m just starting out as an international traveler who likes bringing liquor home as a souvenir. I don’t want to just assume that the Duty Free shop in Athens will have the best deal. But I figured I can set aside any worries if I hear it from you folks.