a few things are keeping 4k prices high, sensor availability for one.. demand is high, and production is low.. secondly, optics.. there is a plethora of cheap optics out there, but as you increase resolution the lack of quality starts being obvious where as lower resolutions it was not.. once you walk away from the bulk of these cheap lenses then the prices go up really quick, ever looked at what optics on SLR's cost? heh.. the cost of the optics become the greatest cost really fast.
eventually the market will adjust, but this industry adjusts at a snails pace.. everything takes long time, that you can bet on.. people dont install video systems every year like they buy an iphone