Aren't most tolls everywhere just in one direction? That way, half the number of toll booths are needed compared to both directions (before FastTrak, etc each lane required a human cashier)

I don't know; I'm no expert on typical tollway designs. I've certainly seen turnpikes that are tolled both ways.

Anyway the number of cars queued up to cross the bridge to the east in the afternoon strongly suggests that road is underpriced.

By implementing another toll gates, they might actually worsen the traffic jam. When I cross the Bay Bridge, i see lines upto the toll booths, and after them, it's usually clear.

Sure if the cost is based on mileage then there would have to be tolls on both sides

They charge you for the privilege to visit SF, not to leave it.

Well that doesn't make any sense either, because there is no toll at the southern entrances to SF on 101 and 280.

I'm not looking for an answer here because I know the answer. The answer is that car drivers are the most self-entitled bunch of externalists the world has ever seen. If there was any sense in this system the toll at the existing toll plaza on the Bay Bridge would have been raised until congestion disappears, but that hasn't happened. On the other hand BART fares are indexed to inflation, because only the riff-raff ride transit.