A few people have mentioned in this thread that duty free shops are pointless. I disagree. I just bought three bottles of gin from LHR and the cost was cheaper than what I can buy them for in the US. Sipsmith London Dry 750ml is $28.99 + TX sales tax from my local Total Wine. The duty free shop sold it for 25.09GBP (or about $30USD) and that was for a 1L bottle with no additional tax. Because I bought three bottles, I got a 10% price reduction.