It's actually cheaper at supercharger, $.26 after midnight, but ~$.50 during off peak at home after all extra fees in SJ, even after selecting EV charging plan.
San Jose resident here, you shouldn't be paying that much. If you have a TOU plan it's something like 35ยข/kWh off-peak and 50 or so during peak times. They do keep raising the prices for no reason but not that much (yet).