http://72.14.253.104/search?q=cache:95RkKeoc-JcJ:irepp.stanford.edu/documents/GDF/SUMMARIES/Imazeki.pdf+per+student+cost+in+california&hl=en&ct=clnk&cd=1&gl=us&client=firefox-a
varies in CA from $5800 to $23800 depending on the district.
Christian schools are not an acceptible alternative for many people. I don't know that it is fair to consider those in calculations of averages (or at least break them out as a separate number).
I think there is a market for "new" private schools. I'm pondering that right now actually...