Kbd mania stuff is expensive because of the case machining and pcb prefab (especially now that they come with smd pre-soldered). Add to the base cost the price of switches, keycaps, stabilizers, lube, stickers etc plus building if you're not handy and $400 becomes comparatively reasonable.
If you don't appreciate the effort, attention to detail and high cost of manufacturing then you probably won't understand the difference. I don't like the fancy sports car comparison; for me a nice custom or a topre is more like a nice tool... If a Filco is Craftsman grade the topre and kr. customs are like Snap On.