HotDog,
I disagree with your premise. Or at least it isn't true in all cases:
I get more or less the same gross salary in Hk as I would get in the UK. I don't get any housing allowances, COLAs or anything like that. The standard of living I enjoy is at least as high in HK as it would be in London - the higher costs of some items in HK (and there are plenty of things which are the same or cheaper) is offset by the fact that I am taxed at about 15% rather than about 35% on my salary, and also by the fact that I do not have to pay any tax on profits from my savings investments.
I simply don't agree - certainly in the absence of kids of school age - that allowances are necessary to have the same standard of living in HK as in the UK.
Note though that "have the same standard of living" is not the same as "live in Hong Kong as if you were living in London".