That’s years worth of baths for most people - average cost per bath at 0.25 cents per gallon would be 7 cents.
Realize farmers use water measured in ACRE feet
That's the cost of living in a desert.
In my defense, it's common "greengrocerese" to list a price that way. If limes are shown as "0.10¢ ea." on a handwritten card, you're not getting ten for a penny.
I still think taxing residential water is irrelevant, and that the difference between buying water at auction from the state and paying a tax for that water to the state, is that auction is better because price discovery tends to be.
This highlight the large water uses (usually free in the millions of gallons).
If you aren't willing to say a gallon of water is worth a quarter of a penny - then we can usually stop talking about any supposed shortages. Retail / urban water use (ie, a bottle of water at the store, often 1/8th of a gallon - this tax is irrelevant obviously) already is wildly higher in cost than the "free" groundwater and river water folks are using.
Residential and city use is a) a drop in the proverbial bucket (20% of California water use) and b) comes from a completely different system. For the most part it's drawn from snowmelt in the Sierras, and even when drought gets pretty bad it's been sustainable. Fingers crossed it will stay that way.
Really it's farmers who should pay for water, and hard limits on aquifer withdrawal. They'll hate it but there's not enough to go around and I don't see an alternative.
Also worth pointing out that California is an enormous place and what applies to the Central and Imperial Valleys doesn't apply to, say, the San Joaquin Delta. There's no good reason to stop growing rice in the latter, because the acre-feet of water which go into doing so are just going to flow directly into the Bay otherwise.
Maybe we could pay for more of it to be diverted into the Central Valley if there was some sort of profit in it. Water auctions, say.