About the valuation of the houses, land and appartments in RI: Sorry to say, but many people pull numbers out of their @ss. It is not based on an objective price for sqm and facilities but purely on; "the lady two doors further is asking xxx billion for her house so ours should be at least the same!". And when someone can't sell his house, he increases the asking price! So unless you see a sales contract or have the money in your hand, takes those 'my house is worth 3x more than when I bought it' stories with a grain of salt. And don't calculate yourself rich.
About the DKI and surroundings: A place like South Tangerang (BSD & Serpong) has still such an amazing amount of free space for the developers to use, they can keep on going for 10 years (in my conversations with Paramount marketing) it is not very wise to invest there for a short term gain. Especially since many people want a new built, not a 3 year old house. If (big if) the Pluit island developments and the Big Garuda get materialized, it would not be a bad place for investment. But Agung Sedayu and Agung Podomoro have quite some issues there. Luckily I pulled out of the Branz and Holland Village projects.