This question already has an answer here:
What exactly does duty free mean at the various airports? Does it mean that the items are cheaper because they have no tax/duty applied on it OR does it mean the item would "not count" for the free allowance amount at our home country?
Just to add, I checked the prices of various items at Doha airport duty free shops (for iPhones, perfumes, etc) but did not find much price difference from what is available in India? So wanted to understand.