Low tuition could be due to competition. I live in the Bay Area, which certainly has a lot of wealthy people and high overall costs. Oddly, private school fees are one of the few things here that aren't insanely high (e.g., compared to a million dollars for a 1200SF house on 6,000 feet of land).
There are loads of K-8 private schools around here --- as in, pages and pages of listings in the small-font full-page tables that Bay Area Parent publishes. I imagine that sheer numbers keep the fees low. Many or most (?) of the Catholic schools charge less than $10K annually (a lot less if you're a parishioner). Many of the secular ones are in the $10-15K range. The high schools are pricier, but there are fewer of them. Even so, that means low to mid 20s for most of them, with the odd small one below $20K. We don't have many of the 35-40K+ schools here. That price point seems to be the rule back east (?).
