The thing you need to look at when considering buying or building a shelter is “what do I need” versus “what do I want”. I am sure all of us would “want” one of the congressional bunkers with all the amenities. And I am also sure that is way beyond affordable.
While I was working as a disaster preparedness tech in U.S.A.F. (United States Air Force), I have seen and evaluated many types of military and civilian shelters, and the only thing those lifesaving shelters have in common is high cost.
Different Shelters, Different Problems
As far as the military shelters go, permanent ones tend to be made of reinforced concrete and are between 2 and 4 feet thick. Most are also built underground and the covering soil is layered with rock and debris to guard against penetration weapons.