stormcloud: looks like none of the follow-up contributors has actually bothered to answer your questions.
First and foremost, the days of the generous expat packages are all but gone unless you're at very, very senior level in your company (across all industries).
Salaries are generally high, reflecting the high cost of accommodation. If you want to live in the traditional "expat" areas of Repulse Bay and the Midlevels, you're looking at paying an average monthly rental of HK$40,000 (US$5,000) for a 2'000sq.ft. apartment. Please note that upon signing the rental agreement, you will have to pay 2 months rental as deposit, plus the first month's rent plus half a month's rent as real estate agent's commission up front - that's a total of HK$140,000 using this example.
Schooling: unless your kids speak Cantonese, you'll have to select one of the (usually good) private schools. My experience was that the cost of a private day school in HK equates roughly to the cost of a boarding school in Australia, so given the quality of life and the opportunities of sports overseas, it makes more sense to board. An alternative is the English School Foundation
http://www.esf.edu.hk/ which charges more moderate fees and, whilst not providing the "status" of a private school, offers quality education.
When renting an apartment, you might want to make sure that it offers a clubhouse (usually with gym and pool). Club memberships (unless provided by your employer) are - like everything that confers perceived "status" in HK - very expensive.
Healthcare: up to you - no Medicare or similar in HK, so you have to go private.
Actual cost of living: this depends entirely on you and your family. If you go local (meaning you go to the wet market to buy your meat and vegetables), you can live quite cheaply. Supermarkets are obviously more geared to expats and more expensive. Here are some supermarket prices:
(HK$7.80 = US$1.00)
Bread (sliced, for toasting): HK$ 7.50
Milk (one litre, fresh): HK$15.00
Orange juice (1.25 litres, freshly squeezed): HK$ 24.00
Grapes (seedless, one pound): HK$ 9.00
Breakfast cereal (corn flakes, 600g): HK$ 25.00
Crab (live): HK$50 to 75 per crab
Beer (local supermarket brands): HK$3.50 per can
Beer (international brands): HK$6.00 per can
There is no sales tax. The only taxable goods are alcohol and tobacco. I know a Nepali grocer in Mongkok who still manages to sell a bottle of Gordon's Gin for HK$75, though.
Big Mac Meal: HK$19.60
If you need any additional info, please email me.