I think affordability is relative. Im currently paying out of state tuition for my son. My wife and I have been fortunate in life and have been able to find a way to pay for him to attend a very good out of state school. My idea of what is affordable is probably different then what others see as affordable. From what I learned here is a rough idea of what the different types of colleges cost, all in, before scholarships:
In State Public - Approx $20,000 a year
Out of State Public - Approx $40,000 a year
Private Schools - Approx $50,000 a year
Ivy League - Top Private - Approx $65,000
Of course this is going to vary from region to region and school to school but its what I've seen. My idea of affordable is somewhere between In State and Out of State. Others may consider affordable less then In State.
It all comes down to the endowments the private school has. Many of the smaller (ie D3) private schools have larger sums of money to pass out as scholarships. Many of them attempt to use the money to bring the cost of attendance down closer to the higher end state universities in their areas. For example, my son was accepted to a very good private school here in the midwest. Normal cost of attendance is approximately $45,000. The cost of attendance at the top university in our state is about $30,000 a year. The private immediately offered a $15,000 a year scholarship to help offset the cost vs. an in state. My son was good HS student but not great. 3.4 GPA with a 25 ACT. I have found that many of the private schools were offering up money up front to help off set the cost differential.
I guess what I am getting at is, you need to determine what is affordable for yourself and then start talking to the schools. Many of the admittance folks are very helpful in helping you figure out what the real cost of the school is. Unless your attending a state funded university don't assume what they post on the website as cost of attendance is what you are going to pay.