It's nice to see that HK is cheaper than Singapore. Honestly what really jacks up the cost of living in HK is the insane property market. HK has a lot of "hot money" (read:dirty money) flowing into its property market from China and it's forming a property bubble. I'm confident that this bubble is going to pop within 5 years because it's simply not sustainable.
Aside from property, other stuff isn't THAT expensive. Although the property market does affect the costs of other goods and services in the city, there is also no sales tax and income taxes cap out at 16% here for income derived from HK. Income that is derived offshore is taxed at 0%. There's also no capital gains or estate tax here.
Stuff like eating out is pretty comparable to any major western city, and HK has some amazingly good cheap eats as well as fine dining too. Computer equipment is really cheap in HK and pretty comparable to western prices. Groceries are going to cost you 50% more than in the west partly due to the fact that there's a cartel that fixes the prices. If you're a cheap skate, you can get around the grocery cartel by shopping at prizemart and your local wet market.
Rent is insane though. A friend of mine was paying 16k HKD a month for a 700 square foot flat. That's over 2 grand US a month. I bought property when the market was cheap though, so I am not affected by this and it's only a matter of time before the bubble pops anyway so don't fret.
I've been living in HK for nearly 8 years now.