I Think it's not a single million dollar is the price of that Zombie Proof house, Considering the Layering and the design inside the shell of that house, definitely it would costs a 10-15 million dollars. (Considering the best materials)
Query: Is it possible to breathe inside, I mean if they close the whole walls? LOL
Well for the Question, Well Stack food enough and stay on that Zombie proof house.
Well if i view that house it looks like conrete walls of 1meter or more that's hughe.
Also at the breathing questen, it's posible to have a device that takes air from the outside and switch it from the inside in cooler air / good air.
I already have seen this house (not in real life) and when I saw it, I thought to myself "Why would anyone want to buy such an ugly house?" I don't see any sence in it but some might buy it eventually.