Perhaps, San Francisco policy is to use parking prices to discourage vehicle use. They haven't gone the London 'congestion tax' route yet, perhaps they will.

There is a difference between what "is" and how the system responds to what "is". In this case I don't doubt for a moment that drivers of self driving cars would use this technique to economic advantage, and yes if it got too bad it would invoke a response (much like the $5 parking meters with credit card readers in them was a response to cars in general).