This is not accurate in my experience in SF. Most of the time, the price is comparable to UberX and during peak-times, the price is upto 20% higher than UberX.
I took a couple of trips for the novelty value (as someone else mentioned, it's by far the best tourist attraction in SF at the moment!). The experience was really great - very relaxing - but there's no way I'd use it if I just wanted transport. I can see women paying a premium for it out of fear of taxi drivers, but that's not really an issue for me. I would maybe pay a small premium to avoid awkward lack of conversation, and the bad driving of typical taxi drivers, but not 50%!
I also hope it will be cheaper, but it's definitely worth paying more for Waymo because of the better experience: safer, smoother, quieter, no weird smells, or conversation, etc.