I'm in FiDi right now (weekday afternoon). A Waymo ride to Dolores Park is $18. UberX is $17. Lyft is $19.85.
I find that late night you often will not be able to get an Uber. I think drivers have been ceding ground to Waymo's obvious night driving superiority.
My experience has been that they are roughly equivalent in most cases. Sometimes they're slightly cheaper, multi-stop routes they tend to be a lot cheaper.
If you tip in Uber/Lyft, Waymo is always more price competitive.
