eternity,
Your maths was a bit off, also some of your other info.
First year SO, once online flying 84 credit hours would get the following
Monthly - $35,170
HKPA - $10,000
Hourly Flying Pay (84 hours) - $3,500
Total - $48,670
If you divide up that $875,000, and add it to the monthly calculated above, you earn $729,875 a year gross. In HKG the first $108,000 is tax free, the total tax liability on $729,875 is around $93,718, you would have a Nett income of around $636,157, or $53,013.14 monthly.
This would be equivalent to AUD$6,855 a month after tax, or around $115,000 P.A. before tax. This is the entry level position.
You do not need 30% deposit, it depends on what you buy. The Hong Kong Mortgage Corporation helps a lot of people out making up the difference between the 70% mark and the 95% mark, all you need to come up with is 5% deposit, and $875,000 would hit that mark. If you were to buy, you get an additional tax benefit of around $100,000.
GovHK: Tax Computation of Salaries Tax and Personal Assessment