It isn't really the absolute salaries that I was commenting on - more the apparent expectation that there should be two different rates for the job, depending solely on whether you move from another country to do it... that's what I can't see any logic for.
If there is a sufficient supply of pilots in Singapore (or Hong Kong) then I see no reason why an employer should pay a premium to bring someone from somewhere else. And if there isn't a sufficient supply then surely the most logical thing to do is to raise the salaries of all pilots employed in Singapore until you reach the point where you do have enough applicants?
It seems to me, naively perhaps, that airline pilots are actually one of the most global of commodities - no language barriers (all speak English - yes, OK, I know that's not totally true), more or less complete standardisation of job specifications (flying an A340 for CX is much the same as flying one for any other airline), and so on.
By the way, as a sometime recipient, I do understand that the expat packages are nice to have - I came to HK on one 5 years ago, and at that time the company in its misguided generosity rented an apartment for me at HK$50,000 per month, and gave me a cost of living allowance on top of my UK salary. They did however also "hypotax" me as if I was still living in the UK. Yes the total package was substantially more than DHL apparently pays people for flying out of Singapore. Perhaps similar (from what I have read) to what a CX passenger captain of middling seniority would get, although without the travel perks and with a bigger tax hit. That was for having P&L responsibility for about US$150M of business a year and managing a couple of hundred people around the region.
But when the telecoms bubble burst (that being the business that I am) this extravagence was not sustainable any more. Now I rent my own place (for HK$20K, but soon to move downscale a bit further). Because of the hypotax impact I'm not much worse off in fact for the loss of allowances - I have an apartment that is more or less identical to the $50K one, albeit without the magnificent view.
As a sanity check on all of this, remember that the average household income in Hong Kong is under HK$20K per month and that people do bring up families quite comfortably on that. I don't have enough knowledge of Singapore to be able to comment specifically on how the numbers work there.