Again depends on your seniority, type of business you are in, where you are relocating from and your personal circumstances. Some firms also play around with your salary and mix and match local status and expat status. Things to consider include:-
1. Housing allowance - given quite often, sometimes may be reflected in your salary. For a 400 sq ft apartment in mid levels 15k should cover you in a walk up apartment, 25k you should get something around 600-800 sq ft in a newer building with limited facilities (porter and lift only)
2. Flights home - offered sometimes to senior people with a family, a good guess to likelihood is how generous your travel policy is when you have to go for work.
3. Health and dental insurance - Common perk for locals and expats alike. The difference would be if you are offered an international policy or a local one.
4. Pensions - There is a mandatory scheme here in HK called the Mandatory Provident Fund which is capped at $1,000 per month from yourself, and the same from your employer. If you are a US citizen or Green Card holder, beware of some tax complications on this. This might only kick in after your first year.
5. Education expenses for children - If you have kids this can be very expensive, also getting a place can be difficult as well. Some companies own debentures in order to help their employees.
6. Tax equalization - If you are coming from anywhere but the US, I would avoid this as it would likely result in a reduction of your gross pay. Tax rates here are low. If you are subject to double tax, speak to an accountant.
7. Visa status for your partner - If you want your partner to come out with you, you may want to apply for a dependent visa for him or her. That way they can look for a job after arrival if they haven't lined up one already. There are plenty of posts on this.
8. Moving expenses - Sometimes you employer will have a direct agreement with a shipping company and will pay direct, other times it will be part of a general allowance.
9. Relocation allowance - This sometimes is a lump sum to cover additional costs (eg new furniture, deposits for flats etc).
10. Termination of home country contracts - You may have additional break costs when moving like your current lease, mobile phone, gym membership etc. This is less likely to be covered but just beware of these as they can mount up, and look at ways of mitigating them.
11. Temporary Accommodation - When you arrive you have to live somewhere. People often get 1-2 months before you have to move out. If you are put somewhere expensive the tax bill might be a bit of a surprise. Also remember if your stuff is coming by boat it take a while to get here and clear customs.
This list is quite comprehensive and you might not get them all. What I would say is to stay focused on the overall package and not get stuck on an individual element. Also consider all the potential hidden costs in moving.