It's a heckuva lot cheaper to build one than to buy one. But what you're buying is somebody elses disaster preps anyway. I'd do the emergency power, radio, secret rooms or a bank valut door (walk in gun vault and an excuse to fill it) as well as the emergency water and fuel tanks and I'd have a better perimeter intruder plan. That's where having been an infantry captain would come in handy.
Yes it would be good to design your own. It sounds like the one I saw could have been designed by you though. The only thing on your list I am not sure that it had was the secret rooms...Although it did say that there were ceartin security measures that would not be disclosed in the add. The place even had security cameras hidden in trees, ham radios, scanners,...the works. The latest charge controllers, battery bank, Air filtration system. Get this...the intakes for the air filtration system were conceiled, but just is case there were back flow valves to keep anyone from pooring something down them.
Then you are going to help all of us build one too right
-wink-