I'd guess the SSD. They're expensive for consumers already, being the new hot tech part to have. Then you have MS with a somewhat custom version, which you would think is more expensive yet. Then SNY with some highly customized super future SSD tech beyond what MS has, which may seem to be, well, super expensive. The rest of the tech shouldn't be all much different in terms of cost between the two, so even if XBSX is more costly in that case, the PS5 SSD would be a big cost that bridged that gap and exceeded it. There is also the question of the PSVR break out box and whether that tech will get baked into the PS5 console hardware or not. May not be much extra, yet another cost to take into account.
If you didn't take into account the engineering SNY does themselves, the mass manufactured discounts, new efficient PS5 manufacturing, etc, it could seem like PS5 may cost more to make. Do they also know the consoles are typically loss leading products?
