How expensive is it to build an underground doomsday bunker?

In short-span of the few thousand years, several human civilizations vanished from the earth due to natural or man-made disasters. The creation-destruction and re-creation is a natural cyclical process, but the inherent nature of uncertainty involved in the process forces humans to be ready for any kind of disasters so that one could ultimately survive for re-creation. This spirit of survival makes all the difference when some catastrophe of varying scale and intensity hit humans. We prepare for any kind of doomsday scenario and bunker is one such preparation in the long list of preparations.

Whether it is man-made or natural disaster we might face the extremes of heat, cold or water our survival will depend on how safely we could face these extremes. It will happen on any particular day, as doomsday theorists predict, or it will be a slow process of mass extinction nobody knows, but one factor …