Unfortunately property has no fair value, due to a few factors,
1) the land price, developers are like bakers, if the flour they buy is expensive, the bread they sell will be expensive, if all bakers sells their bread expensive, there is nothing you can do, unless you want to bake your own bread
2) public confidence (property price is just a reflection of this confidence)
3) raising inflation, there is a fix cost of sand, cement, steel, copper that
is required, and with raising inflation, so is cost of constructions
While it is possible to somewhat factor in point 1 and 3, public confidence and government policies are hard to calculate..
In a normal environment, with no recession and decent stock market, property prices will naturally appreciate.. especially with population growth, which cannot be stopped