There should be other considerations as well. I understand your apprehension, but giving the schools names or at least where each is located would help people give you solid advice. Even tier 3 schools can have major differences in various factors. Remember that where you go to school, especially a tier 3, would mean that's where you would more than likely practice.
Also, I would want to know, why is the one school HALF the cost? Is it a state vs. private school, or did you get some kind of scholarship? In the latter case, you could try to bargain with the other school to get a better financial offer