Don't forget you need to pay tax on the education allowance and make up the shortfall between what Cathay pay and the actual fees (which can be substantial if you don't get an ESF school place). It all adds up... Times that by 3-4 kids and you get the picture.
Couple that with the tax due on the housing allowance (treated as a cash benefit by IRD if you use it to pay a mortgage) - with govt rates, rent and management fees on top, and you find that a rather large chunk of your income goes before you see it.
Just sayin'...