Hello Shalini,
Answer to your questions is it depends; primarily your lifestyle and the quality of life you would like to maintain will have a huge impact on your costs. When I moved to the Philippines (albeit living in Pasig and working in Makati) these were my real costs. Again, you may want to adjust depending on your lifestyle expectation. It just comes down to "need" versus "want".
1. Housing (3 bedroom townhome in a gated community) USD 2,000/mo
2. School - my daughter was in 2nd grade and decided to put her in an international school. This is really where you'll have to decide whether the local system is sufficient for your child's education as the costs are substantially different. If you choose a local school expect to pay around USD3,000/year plus incidentals. I would budget around USD5,000/year to be safe. My daughter's school. on the other hand cost us USD9,500/year plus incidentals. We probably spent around USD11,000/year in the end.
3. Food/groceries - To put this in perspective, we are 4 in the household plus our housekeeper (our chauffer bought his own food but we still fed him breakfast as I have early morning meetings). I would budget at least USD1,000/mo.
4. Utilities - this is what was unexpected for me. It is hot and humid all the time and depending on your tolerance for heat, you may want an your a/c on 24/7. Room AC is the most practical. But if you want the option to centralize AC, you may want to budget a lot more. Depending on use, I would budget around USD500-600/mo including hydro (electricity) and water.
5. Medical insurance - make sure you get this. When we first arrived, there were a lot of vaccine that were not a requirement in North America that were mandatory in Asia. I spent at least USD20,000 in medical expenses in our 3 months. For a family of 3, expect to budget around $500-600/month for premiums.
6. Auto- the Metro area is extremely polluted. Make sure you have at least 2 cars. 3 is ideal due to the coding system of traffic in the Metro area. You can save on this if you choose a location that maybe close enough to your work area and would allow you to walk indoors as opposed to walking out. I would budget USD4,000-5,000/month for two cars, gas, and insurance.
7. Household help. If you want to get a nanny or chauffer, a good nanny would cost you around USD300-400/mo and around USD 500 for chauffer(I know, its unbelievable that live help is actually the cheapest expense) .
8. Incidentals - depending if you want to see the country-side and travel and how often, I would budget around USD5,000/year.
If you want the above lifestyle, budget around USD10,000/mo. You can live for significantly less. But I chose that lifestyle as Manila is such a dump and would only move to that city if I could maintain my North American lifestyle as best as I could.
Hope that helps.