Well, usually sales tax is not that bad gei, in WA, we have minmun 7% sales tax, but in my county is total 9.5% sales tax. and bus fare, raw food, etc etc, doesn't need to get tax....at least we are better then Canada which they have a total of 15%.
Also, for travelers, if they can get a refund of sales tax when they leave HK, then It will not be that bad.
But most of the countries that have sales tax, if your income level is lower then the acceptable level, then government will give you a food stamp (or food vulchure) for a certain amount of food everyday (means certain amount of $). maybe HK can use that as an options.