In terms of cost… most colleges have an Estimated Family Contribution calculator on their websites, which will give you an estimate of how much that college is likely to cost for YOU; most good colleges give financial aid to students who qualify based on family income and assets. So “average cost” means nothing, but the EFC for you may be helpful.
In terms of graduation rate- I never went searching for this per se, but I see that all my son’s prospective colleges have really high rates. I guess it goes hand-in-hand with the other factors we sought. If your child’s graduation is a concern for you, yes, look for a graduation rate over 80%, but also look into what support services are available at the school.
I cared most about the student body’s being very capable, because intellectual conversations with peers in and out of class are a bigger part of the college experience even than having great professors. Diversity is important, too. I also cared about class sizes (see the info on their common data sets), opportunities to work closely with professors, attention to a freshman experience to help students become socially connected, ample opportunities for extracurricular activities and research and nice on-campus housing and dining (basically, a school that has great resources available for the kids). Those were some of my initial criteria; my son’s observations and feelings shaped the list.
If you can visit, that helps. My son definitely developed his own ‘feel’ for schools and the type of college experience for which he is looking.
Also- you mentioned ranking the choices, but you want your child to have favorites among reaches, among matches, and among likelies/ safeties. You want your child to be happy and excited when the admissions letters arrive, even if there are some rejections among them.