I believe this is primarily attributable to the cost of housing, which is high because of several factors:
1. Proposition 13, which limits property tax to 1 percent of the value of the home, and allows increases in property value to only 2 percent per year. (Taxes actually come out to 1.25 percent because of other fees.) This inflates the purchase price of housing above high-tax areas, like the state of New York.
So it qualifies as a result of governmental policies. correct? Or do the actions of the voting public not qualify as "an act of governance" in your book?
2. New housing is difficult to build. Partly because of government permitting and zoning, but also because of terrain (most of the flat areas in San Diego have been developed already) and water availability. (I know large segment of the San Diego back-country is zoned for large parcels, with the requirement that most of it is undisturbed in order to maintain the water quality for the back-country dams.)
My understanding regarding a LOT of the "San Diego Backcountry" has to do with a few things that are related to what you mention. But not exactly in the way you try to make it seem. Most of the "Back Country" is
not on Municipal Water, which means the homes being built require their own water rights, or access to somebody else's water rights. Lack running water would tend to greatly restrict the ability of a person to live in a particular area.
Likewise, as they do not have access to a municipal water supply, that likewise in turn means they are not hooked into a municipal sewer system. Which in turn means they're reliant predominately on Septic Systems, which again, given considerations for the prevailing climate in the area, and the resulting soil types(it isn't very "loamy"), the drainage requirements for those septic systems is rather large, as that is necessary to prevent the septic systems from excessively polluting the area water table(as they mainly use ground-water).
That being said, you introduce a municipal water and sewer system into an area, and suddenly the number of housing units you can build on a 10 acre plot of land increases considerably almost as if by magic.
Of course, to first build that water and sewer system into that area, you have to go through a very extensive and expensive environmental impact assessment process, then numerous other reviews and a number of other road-blocks geared towards preventing development and "urban sprawl" into outlying areas that are largely unique to California alone. A cost that of course find itself "baked into" the cost of whatever housing ends up being built in that new development.
All things being equal that typically translates into only high-value housing developments being built, as the developer wouldn't be able to "recover the cost" if they built homes catering to the lower-income or lower-middle-class income brackets.
But then, this particular problem is becoming common nationwide due to increasingly strict EPA requirements, however California trends heavily towards going much further. Which is all well and good, California's Governmental entities should have a better grasp of "Reality on the ground." Than the federal side does, as they should be going for "one size fits all" (Which means it probably fits none in practice) in theory. However, it still cycles back to "California has policies and practices in place, which are unique to California, which makes building "affordable housing" a non-viable option in
most cases.
3. Labor is more expensive, because the cost-of-living is more expensive, because housing is more expensive. (A bit of a feedback loop there.)
4. This is a desirable place to live because of the mild climate. (I went bicycling yesterday in shorts and a T-shirt. Anyone else do the same?
)
See above, and #4 is a valid point that all things aren't entirely equal. However, the Gulf Coast in general, while it can hardly boast "mild" summers, their winters tend toward what the rest of the country, and even California, would consider "mild." Trade off is they don't have to worry as much about their house being burnt down by a wildfire, or destroyed by an earthquake or landslide.
While government can influence a couple of those factors, it has no influence on the rest.
In a government "of the people, for the people, by the people" the government controls all but one of those factors(Climate). As you pointed out that #'s 1 and 2 directly impact #3.
The mild climate also allow people to live "on the streets" more comfortably than in harsher climates, like, say, Buffalo, NY. 
And let's not forget the second- thru fourth-place finishers: Florida (R) at 19 percent poverty rate, and New York (D) and Louisiana (R) at 17.1 percent.
So, between the factors out of government control and the fact that both Republican and Democratic states have similar higher-than-average poverty rates, I don't see how anyone can blame California's high poverty rate on its governing party.
Ok, let us stop and back this up a little bit. Florida may have been "reliably Republican" for some time now at the state Government level, but that is a bit of a misnomer, don't you think? Louisiana is also false claim against the Republicans. Or are you forgetting that the Democrats were in control of the state when Katrina hit? So two of your four examples cited are more (Democratic) Purple than (Republican) Red, when viewed in proper historical context.
https://en.wikipedia.org/wiki/List_of_Speakers_of_the_Florida_House_of_RepresentativesSeems to indicate that their House of Representatives was in Democratic Control from 1875 until 1996(and also note: That is ninety-six, not sixty-six). Yes, the Republicans have held the Speaker Seat since, but they're having to contend with "legacy" issues in Florida that once rolled out, are nearly impossible to roll back on the political stage.
And just for completeness on things, sadly the page for the Florida Senate President page isn't nearly as complete or comprehensive, but I did find this:
https://en.wikipedia.org/wiki/Ander_Crenshaw#SenateHe returned to public office in 1986, winning a special election for a seat in the Florida Senate that he held through 1994. He became the first Republican elected president of the Senate in 118 years in November 1992, but agreed to serve only one year instead of the usual two, as a compromise between Republicans and Democrats who were evenly split in the Senate that year.
I'm unable to (easily) tell if there were any further power hand-offs between parties from 1993 onward apart from at least one additional obvious hand-off back to the Republicans after 1993(as the Republicans hold the office now). But 118 years previous to 1992 would put things back to 1874, a year before Democrats took back the House in Florida in 1875. So the Democrats
had 117 years of unbroken legislative control in Florida, compared to just over 20 years for the Republicans?
Now let us look at the Governor's seat...
https://en.wikipedia.org/wiki/List_of_Governors_of_FloridaI see Democrat Governors from 1877 until 1917 when the "Prohibition" Party took the seat for years, Democrat control resumes in 1921 and continues until 1967, when the Republicans hold it for a single term before reverting to the Democrats in 1971 which continues through to 1987, where another single term Republican comes along. Then it's back to the Democrats from 1991 until 1999 when "Jeb" takes over the Governor's seat. Which in turn leads to Charlie Crist who served one term as a Republican, and a second term as an Independent. Rick Scott(R) has held the seat since 2011.
So realistically, even assuming the Republicans controlled the Florida Senate since 1994/1995, they were contending with a Democratic Governor until 1999. So they've only truly had 17 years to try to undo/alter
over a century of Democratic actions in Florida. That matter also tends to suggest that a "Florida Republican" probably has a lot in common in the New England flavor of Republican, or the California type, rather than the Republicans you're likely to encounter in "flyover country." (Particularly given that Democrats are reasonably certain they're going to "get Florida back" under the Democratic Banner in the coming years.)
Also, it should be noted that out of the four states you mention, Florida comes the closest to matching California in terms of year-round climate, so item #4 IS a factor there, as well as item #2, just on the other extreme, given that most of Florida is practically wetland.
New York doesn't really require further examination, it's basically been Democrat Central for a very long time.
But let us look at Louisiana. To change things up, let us start with the Executive:
https://en.wikipedia.org/wiki/List_of_Governors_of_LouisianaFrom 1877 to 1980 we see an unbroken chain of Democratic Governors. From 1980 to 1984 we see a Republican in office. The Democrats regain the office in 1984 and hold it until 1996. A Republican obtains the seat in 1996 only the lose it in 2004(Just in time for a Democratic Governor to make a mess of the response to Katrina), where the Republicans then claim the office for two terms from 2008 until 2016, where it then is held by a Democrat once more.
Wait, I thought you said Louisiana was Republican Controlled? I'm seeing a Democrat holding the Governor's office... But from this, I'm seeing Republican governorship that doesn't happen for longer than 2 terms(8 years), and only going back to 1996. Even being generous and including the 1980 to 1984 terms givens Republican control of the Governor's office in 20 of the past of 38 years. That seems rather Purple to me. Of course, that's nothing compared to 20 years of Republican "leadership" against a backdrop of 121 years of Democratic stewardship.
Well, let us dig further. On to the Legislature! Where:
Democratic_Domination_(1877-1976)Presents an issue as per wiki:
From the end of the Reconstruction in 1877 until the appointment of John Hainkel in 2000, the senate chair was held by Democrats.
. . .
The reinstatement of the elected senate presidency and the installation of a new constitution brought with it something Louisiana had not seen since the 1850s; a two-party system. Also new to the presidency the practicing of appointing of the president by the Governor. This practice had been applied to the state House Speakership for years. In 1980 something that had not happened since the Reconstruction became a reality; a Republican governor was in office. David Treen was elected in 1979, and with him came more Republican legislators, although only an enlarged minority, and in 2000, although still in the minority, Republican John Hainkel was appointed by Republican Governor Murphy J. Foster, Jr. to be senate president, the first Republican in over a century. In 2011 the Republicans obtained a majority in the senate,
So where the Senate in Louisiana is concerned, Democrats held a majority from 1877 until 2011. That's quite the impressive run. Of course, that means that they(Republicans) only held the Governorship and the Senate from 2011 until 2016. A whopping 5 years! Yeah, they're totally going to undo 144 years of legislative action in such a small time frame. Of course, there still is the lower house.
https://en.wikipedia.org/wiki/List_of_Speakers_of_the_Louisiana_House_of_Representatives#List_of_SpeakersWhere surprise, surprise. Democratic Speakers of the House starting in 1877, and running up through 2008. Republicans since. Oh wait, one more caveat from wiki:
In 2008 Republican Governor Bobby Jindal appointed the first Republican speaker in over a hundred years even though the Democrats held a small majority.
So it does look like there has been a fully Republican controlled legislature in Louisiana since 2011, and a partial one since 2010. But that ignores the matter of Democrats having a lock on both legislative houses from 1877 until 2008, the Senate President being a Republican despite a Democrat Majority in 2000 not withstanding.
So just how "Republican" are Florida and Louisiana again?