I work in manufacturing. I have a pretty good idea what an aluminum sand casting costs, plus a marble top, and it ain't nearly that much. Why can't they be pumped off an assembly line?
I suspect you are right. A large part of the cachet of these modernist pieces lie in their exclusivity and high price points. Just for our information, can you please tell us what in your estimate will be the raw materials + manufacturing costs for making a Saarinen table? Or a plastic + metal chair like the ones Kartell, Knoll, Vitra, etc make?
Once we have that info, adding royalties, distribution, and ad costs, we can estimate the profits those hi-design companies are making off our backs!