Another thing to add to the mix, I suppose... lots of HK people live in public housing or own their homes outright.
There is a homework centre near ours and I have been able to crunch the numbers (I know his rent/overheads and I know his students and how much they pay) and I reckon he and his wife net about $10000 per month... that seems to be enough for them.
Could be that on $1000 p/m rent, eating a diet of gruel and noodles, you just don't need as much money.