The article you cite says that the prior single payer bill that failed in 2017 would have cost an estimated $400 billion in taxes per year. Or, roughly $10,000.00 per resident per year. Who exactly is going to be paying that? Because mind you, California’s budget is presently $200 billion, and we have the highest taxes in the nation, with only property taxes remaining somewhat sane. We have a high state sales tax, high state income tax and Capital gains tax. Even if the cost is over-inflated, and would only be half as much ($200 billion per year), we would have to double California’s tax revenues.
Left, right or center, Californians are not clamoring for being taxed more. Especially not when the Californian state governmental bureaucracies have demonstrated themselves to be sluggish morasses of ineptness, even when lives are on the line.
As of 2019, the American health care system costs $11,582 per person. How do you finance a system that expensive? Well, we're already doing it! That $200 billion may be net new spending
by the state government, but it's not net new health spending in California. Those hundreds of billions of dollars are already being poured into the health system in that state, financed by the same households, businesses, and government entities that would be financing the state's single-payer program.
State-level health spending numbers haven't come out in a while, but let's take the latest national health spending numbers (from 2019) and imagine California's corner of the American health system more or less mirrors the national numbers.
So if total health spending is a dollar, households are financing 28 cents of it and businesses are financing 19 cents of it directly through premiums and out-of-pocket spending. Another 45 cents of that spending is being financed by various levels of government, which of course in a deficit-less world ultimately derives from households and businesses again via their tax contributions.
Those entities are all collectively pooling their funds and passing them through private insurers, programs like Medicare and Medicaid, and sometimes (for households) just paying directly out-of-pocket. Those payers in turn are taking that money and cutting the checks that represent the revenue stream to health care providers, like hospitals and medical professionals, with about 7 cents of the health care dollar siphoned off along the way by insurance and government administrative costs.
If California were to pursue single-payer, the entities pooling their money to purchase health care are the same. The same households, businesses, and levels of government will still ultimately be the ones purchasing health care. But instead of filtering through a variety of different payers, all of their contributions instead get collected as tax revenue by the state government and turned over to the state single payer (significantly oversimplifying, as for instance out-of-pocket spending is unlikely to disappear entirely and I imagine the federal contribution would still be collected from households and businesses by the feds but would then be transferred to the state single-payer entity).
So in principle you can imagine a California single-payer system in which everyone pays the same thing they do now, the only change being who they pay it to, and the same revenue flows into health care providers from the single-payer entity.
Obviously the reality is complicated, since there will be various distributional effects; there are a thousand technical, operational, and policy details to address; and the transition is likely to be incredibly challenging (precisely why I'd like to see a state experiment with this model). But to a first approximation, the answer to questions about who pays and where the money comes from is: the same people and entities pay, and the money is
already there.