When we were in Virginia, the campground made us post a $100.00 deposit for electricity. We were there three weeks and got $68.00 back. One thing I learned is that I should take a picture of the meter when it's installed and when it's ended. I don't believe it is legal to make a profit on the electricity you use, that would make them a provider and will be regulated like any other utility provider since basically they are buying and reselling electric services.
You should be able to look up the rates for providers in the area you are staying and the phrase "the highest amount provided by CA law" means to me that they may be charging a rate they found for somewhere in California other than where you are staying.
Best way to combat this is to leave a review on some of the websites (like https://www.campgroundreviews.com
)about the campground possibly overcharging for electricity.
I always check these reviews (trip advisor also) to find out if anyone had any issues. Good topic, thanks for posting it.