That is the question I have been asking myself lately! I attended a priave school, and have the loans to show for it! As ecoggins said below, in many cases your cost of attendance can be lower since there are so many scholarship and grant opportunities available.
For me, I think it was worth it not because of teh classroom learning which took palce, but because of the many connections I had outside the classroom and the various opportunities I had to attend service trips, various speakers and seminars, and get involved in a lot of activities.
Sometimes the networking can be very powerful too as ecoggins said, particularly in certain industries. If that is one of your determining factors, I'd say look very closely at what career service and alumni services offers. I have been a bit dissapointed by my college's career services office. They sent us tons of emails junior and senior year about internship opportunities, on campus recruiters etc. but 90% of them were marketed at business majors, which left the rest of us out to dry.