Real Estate Prices in Mumbai

Mumbai real estate prices are ludicrous, Resident buildings are rising higher and higher while there is not one commercial building of even 5 stories. 90% buildings on the outer area are stark empty. Yet their prices are 1 crore. 

Please O please tell me who is of any sane mind buys an apartment as an investment when anybody -- just anybody can build dozens of 10 story buildings right in the same area.

Real estate prices in navi mumbai have doubled in some areas around nerul & kharghar and have tripled in areas like vashi & Koperkhairne in just 5 years. Does this sound like the Sun is shining too bright on real estate in mumbai?

let me just note the reasons for further price increase and/or decrease.

Increase:

1. Higher Population than China in next 15 years.
2. Devaluation of Rupee in the future. 
3. Interest rates could down for a couple of years, which increases the real estate prices.

Decrease:

1. Indian economy is not going to do well in the future. (point 2 in Increase)
2. If economy does do well in the future, it wont be due to IT, which would mean manufacturing and production would be carried out outside the city.
3. Demand, I dont see much demand in the housing, As mentioned above most of these buildings are unoccupied. Supply, there is just too much of it.