I presume you mean to say why California is so expensive. There are many factors that contribute to why cost of living in California is high. Most parts of California are not livable, this causes a short supply in the housing system and therefore, leading to high rents and buying houses are not cheap either.
The tax here is high too; this is many because of the cost of maintenance of Government infrastructures and services. Business and organizations have to increase the prices of their consumer goods in order to keep pace covering their tax.
California is high on everything it seems. From the rent or price to purchase a home there to the food and gas. The reasons are many actually. But the main reason is said to be due to its coastline topography. It is more desired, for one. It is also more expensive to build in such a place. Plus, the jobs offered there tend to pay a pretty penny to people so for those people at least, can afford the prices or at least tolerate them.
And, some of it is the fault of the citizens like the ones who just approved a bill which made it possible to charge outrageous prices like for gas in Death Valley. Sometimes the Liberals don't realize what they are getting themselves into it seems.