I guess it's really, really important for San Francisco to build more housing for the very rich because there's just such a profound need for it. In fact, the demand for million-dollar condos is so high, and the supply so tight, that the folks at Rincon Tower (which is hideous) are bringing in celebrities to try to sell the last few units.
You don't find many mid-range and affordable units sitting on the market; in fact, there's a long waiting list and a lottery for affordable housing. Because there's more demand than supply. On a policy level, one would think that the city would seek to match supply and demand (since the free market clearly isn't doing it). But no: SF continues to approve housing for people who don't need it and won't balance that out with the level of affordable housing that IS desperately needed.