Based on the C scale contract.
You get an education allowance per child of around $70k per year.
As you don't get housing you qualify for rental reimbursement as a tax deduction against your salary, provided your rent is less than 1/2 your base salary. In practice, the total paid in rent for the year is deducted from your total taxable income...or another way of looking at it is you get a 17.5% discount on your rent.
You get additional tax deductions for each child $100,000 and if you are married $264,000.
Rent in Kowloon for a 3br 950sqft saleable is around $30k per month. A car park varies but my building is $2k per month.
So if you got $100k per month and paid $30k in rent and had 2 kids at school, around 8k after subsidy and a helper for 5k. You would be left with around $57k.
Tax wise you would get a rent tax deduction of $360k,plus the others deduction stated above and your tax would be around $85k for the year with 2 kids. (7k per month)
So this would leave you around $50k per month.
These are rough figures...