I don't have the data in front of me, but iirc, its kind-of your standard pareto. Around 20% of the users use 80% of the water in a district. I mean you say no one has the money, but that 20% might be 2-3 oom higher in total use than the median of the 80%.
I think there are two or three issues bundled into one here. One is that water is managed at the district level. Districts are a patchwork of county, city, and private entities, some with elected leaderships, some with appointed leadership. The state has no direct control over water use in this way, although they have significant authority in other ways that can very much impact water use. However, that authority is split between a set of state agencies that have research and policy power, but no regulatory authority, and an elected/ appointed state water board that is just chasing the next election cycle. Finally, at the district level, these organizations are just a hot mess. Its a complete clusterfck of frankly, shockingly arcane methods for assessing and managing water (ever heard the term miners inch?). Half of these districts barely know where their water is going. I see the whole mess as a failure of neoliberalism, an undue faith in markets.
Yes, it's absurd to think about charging ex. $50k a gallon for gallons over 10k, but that's basically a cap. No one has the money.
(But yes, I'd say we should implement caps rather than being ridiculous)