What is a Life Really Worth?

It confuses me over and over and over again, I have not been able find an answer to it. I was just reading CNN and it has a little link that says "Faces of the Fallen". They are just a picture on a website for some and for others beginning of the end of their lives. How does one quanify the worthness of a life? Why arent the first daugthers figthing the fight for Iraqi freedom that their father so strongly believes in.