Duty-free
In the 80s and 90s, when I was flying every few days, I accumulated quite a selection of exotic spirits and liqueurs, I could make you just about every cocktail you could ask for. I particularly remember an AirBaltic flight out of Riga where vodka worked our as US$ 1.75 a litre.
These days, I walk straight past the shops as it seems duty-free is no cheaper than duty-paid outside the aeroport. The last major purchase I made was a Psion Sreries 7 computer (I still have it) because flying to Brussels, having a slap-up lunch, and flying back was cheaper than paying the VAT.
Do you still shop at aeroports?