I guess it depends where you look. Yes, Erconas are cheap, but at least in Germany many ikontas and other folders can be found for not much more. I paid around 80€ for a 6x6 Super Ikonta about a year ago, which works like new. And I saw similar deals later. And of course the non-rangefinder models are cheaper.
Here in Canada, I see ads for basic Zeiss Nettars for above $300, so more then twice what I paid for the Super Ikonta.
About the story of the Ikonta: I read somewhere the lenses came from Jena, the shutter from Munich, these were combined in Dresden, and shipped to Stuttgart for final assembly of the cameras. Zeiss Ikon was a highly integrated company.