Presumably the increased supply of "drivers" going to SFO will lower rideshare prices for everyone and make public transit less appealing

Public transit connections to SFO are shit-tier. Rideshare prices have little to do with it.

I've taken BART and it's fine but expensive (there's an airport fee that's something like $8 per ticket each way). For groups/families I could see rideshare winning on both cost and convenience.

You can BART from there to downtown, that beats a lot of cities. (yes, yes, BART quality can vary, but still.)

What about the rest of the Bay?