First you have to design the camera, designers don't work for free. Then you have to design the tooling, again tool designers don't work for free. Then you have to make the tooling, toolmakers don't work for free. Then you have to source materials, materials are not free.
Also prototypes are not usually made on a production line, they are made in companies' research and design centres as 'one offs'. Even with modern CNC technologies, there is still a lot of cost.
I worked in Ford's Dunton Research and Engineering Centre in the late 70s and early 80s as a draftsman and design engineer. I have used this process from beginning to end. I can assure you 'tooling costs' for a new product, especially one as complex as a camera, are not minimal.
Andrey, This looks to be a high grade folder, possibly on an aluminium chassis, who knows what the top and bottom plates are made of, brass, titanium? I very much doubt it'll be a 'plastic box'.