In Hong Kong, space is premium. Rent, both residential and commercial, is horrendous. And when you rent premium space like Harbour City, you are paying north of $7000 AUD a metre.
Because of this, Watson's is simply non-competitive price-wise. It is a chain designed for tourists or those wanting to grab a bottle to have with lunch or dinner somewhere. Similar story to Etc wine stores. There are very very few retail wine shops in HK that offer serious bargains. Almost everyone, myself included, deals pretty much exclusively with the e-tailers, of which there are literally hundreds. My advice to anyone travelling to HK and wanting to buy wine is to go to Wine Searcher Pro, type in the name of the wine you want, and send an e-mail to the merchant that stocks it. They will happily deliver to your hotel room, and the price is usually 20-30% cheaper than Watson's and the like.
HK is incredibly cheap for wine, incredibly cheap….. but you need to find the right merchant. As you will see in Wine Searcher, any given wine can vary in price by up to 100%!!!!!!!!