Hi, I am an Asia expatriate and am current back to live in Hong Kong. I have shopped my camera gear here in Hong Kong many years now.
Best stores are the Wing Shing and Man Shing chain, same company different names. There are two Wing Shing stores and one Man Shing store in Mong Kok. They have good prices, can be trusted and sell genuine products with warranties. This is where most Hong Kong people also shop, that is why they are now big. If I recall correct, for Nikon products digital cameras have Hong Kong warranties, while the lenses are with international warranties, but please check.
For reference of prices, not affiliated with Wing Shing or Man Shing, see here
http://www.ygdragon.net/index.php?page=photo/cameraprice.htm (actual prices vary some)
In non reputable stores you will stand risk at not getting complete new product or products with Japan or store only warranties.
If you live in USA it is better to buy from B&H or similar since prices do not vary much and you have USA warranties. For people in other countries, prices in Hong Kong are about 2/3 but vary depending on product.
If you have questions, feel free to email me.
Regards
Anders
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EXPAT WITH A HOBBY
Photo Aspiration - Artistic Pointing of Camera at Natural Light
Engineer and Architect - Aspiration of Arts in Technology