Screens and cameras aren't even that expensive and give manufacturers something to point to as a "feature" with a ton of markup.
I think it's more about legacy companies dragging their feet and also spending billions to develop a single car and wanting to recoup all that money immediately. This is where all the 'losses' come from that companies like Ford whine about. In reality, once they get these first few generations of EVs figured out, future development should be a lot cheaper as they won't be starting from scratch in completely unknown waters.