There's also the custom-made PSU and thermal design you gotta put into it as well. Those won't make up the remaining amount to get to the cost, but it shouldn't be left from consideration. Apparently it took a ridiculous amount of R&D to get it to function inside that small form factor (according to a Gamersnexus video I watched when it was announced).
That said, I have no fucking idea who in their right mind is going to buy this. Maybe someone looking for a lower-end gaming PC?