They sell iPhones in the HK airport?! All they got in the US airports are McDonalds, other crappy restaurants, duty-free alcohol, and bunch of rip off "convenience" stores.
I purchased an unlocked unit at the HKIA last January. At the time they were bundling a screen protector, a battery pack and multi charger kit and their price for the 32GB 3GS bundle was HK 7,599. They would not sell it without the bundle.
They give you a receipt from Fortress - a well know electronic store chain in HK. The operator at the Airport is Sound and Vision - a Nuance Watsons store. Their web site: