The average price of electricity in California is 27 cents/kWh, or $270/MWh [1]. Some of this go to middlemen, but some to producers. I don't know the split, but let's say it's half and half.
Diablo produces about 16000 GWh of electricity per year [2]. At $135 per MWh it comes to $2.2 BN/year, or $11 BN for 5 years.
So $6 BN is not quite highway robbery.
[1] https://www.eia.gov/electricity/monthly/epm_table_grapher.ph...
Incidentally, $0.13748/kWh in generation costs, with an increase of only $0.01/kWh for exclusive wind/solar sourcing.
Even the $6B here amounts to roughly $0.08/kWh, which is far higher than the alternative uses of the money.
Electricity is expensive in California not because we use renewables, but because we have not switched to them, and because PG&E has astronomical costs for its grid. We need CPUC to start pushing back harder here.
Even five years ago, PG&E estimated for new solar was less than $0.06/kWh, and they tend to overestimate these things, and underestimate the rate of cost decreases with solar.
In evaluating the difference between maintaining an existing nuclear site, or building new solar, the new cost is the more accurate estimate.
If you look at new solar deployments in California, nearly all include storage, because it increases profitability to be able to deliver during the evening. Storage is profitable today, meaning that it necessarily costs less than market rates.
Price in the middle of a sunny or windy day can be way less.