It's amusing that this was at the Warner back lot, which is out in Burbank. Not Paramount or Universal, which are both in Hollywood. It would have been embarrassing to do this at Paramount or Universal, because those are in Waymo's service area. People would have arrived at the event in real self driving taxis.
Waymos however need thousands of dollars of hardware to achieve this and only work in limited areas. Tesla's bet is a lot more risky but also with a lot more potential.
It's much much easier to make an existing thing cheaper and better over time.