I understand what you are saying about the true cost of a quilt. And in a few instances I can see where it might be helpful to know actual cost (like if someone commissioned you to make a quilt for them).
One thing I knew before I even made my first project (a Christmas tree skirt) was that quilting could become an expensive hobby. I love making the tops and quilting them, but for me the pleasure is in the process. My husband understands and encourages my hobby so, I will just keep my sewing maching humming along and not worry too much about the costs. JMHO.