According to Popular Science magazine (which never seems to do fact checking) article on Kamen this month, the house is 32,000 sq feet.
Give me a house 20 times the size of my home, and a few millions to equip it, and I will have a great shop too.
I note in that the pictures show a lot of things on wheels. I guess even with all those resources you never quite know where you want your tool chest to be.
Daniel