@tumutanzi, my friend. In our country, we also face such kind of unpleasent shopping in the airport.that's why i check the online price befor purchasing anything in the airport.if the online price is quite tends to the purchase price in the airport then i buy it.if it isn't i always careful to carry the things before going to the airport.it doesn't mean i am tightwad, it means i want to have it in it's reasonable price.
You are a smart buyer. I did not realize it, but I will bear your experience in mind in the future.