The state would need to "find" ~$50 billion or ~$1,300 per resident more to fully fund this.
Personally, this seems like a relative bargain and some modest extra taxes should offset the difference. Article reads pretty poorly and sensationalist.
Not to mention that the missing amount is less than most people have in various deductables and co-pays already.
EDIT: Turns out in 2015, per capita health spending was $9,990 already, which translates to ~$390 billion for 39 million Californians. So $400 Billion is cheaper than what we already spend in 2017, assuming modest growth since 2015.
Further, if we assume that this money already gets spent, just not very evenly, we'll end up with a much fairer system and a lot smaller downside for people if/when they get sick.
Personally, I'll gladly trade some immediate savings for long term protection from not having insurance when I need it most. The data seems to imply that I won't even have to pay all that much more.