I think you are confused about what they are actually producing... The beta camera was never meant to be a fully functional cinema camera and should be treated more as a developers kit than a retail product.
Apertus has already completed the first stage of development by building a prototype (see Axiom Alpha) capable of producing images.. The purpose of the crowd funding was to raise capital so the core team could take their current prototype and create a developers kit to expand their community of developers. The 350 euro donation let's Apertus know that not only do you want to support this project but also want to actively participate in future development by purchasing a developers kit for an additional 1900-2300 euro. Apertus is saying thank you by assembling these kits for only the cost of parts which I assume is why it seems unreasonable to produce a camera of these specs for so cheap.
I seriously doubt many will purchase the beta model at retail when it's completed because it's not really intended to be a product. Sure, you could use it to film a movie but there are better and cheaper solutions out there. I think your comments are more geared towards the Axiom Gamma stage which is what the crowd funding/beta is the first step in.