Because you still have to pay for enough fossil fuel generators to power the grid AND the solar and wind subsidies, because the latter can't supply power all the time. If every solar setup had to provide guaranteed minimum power 24/7 for 30 days, then you'd see the true cost is much higher because they would need to directly pay for a mostly-idle power plant, instead of the very inefficient way we do now (brinkmanship of grid stability and occasional massive spikes in wholesale cost).

In WA we pay more for "fish mitigation" than all other hydro-related costs. I expect CA has similar money pits.