Berkeley and taxes

I started listening to a course in American economic history from Berkeley.  In the first lecture, the professor, J. Bradford Delong notes that the students are paying $10,000/year for their education.  This
amounts to California taxpayers covering $20,000/year of each Berkeley student's education.  He then notes that the bulk of tax money comes from people making $70-80K/year, and that the Berkeley students can expect to earn more (perhaps much more) than this.  What rationale can be given for such a bargain?  Delong's conclusion is that each Berkeley student has a social contract with the residents of California to work hard, and to do good work.  I thought this is a nice message.