As an example of an especially articulate use of this analogy for the Atonement, here is Shirley Guthrie (1927-2004), longtime professor of systematic theology at Columbia Theological Seminary:
If God loves and forgives us already, why atonement at all? Why did Jesus have to sacrifice himself to “pay the price”? Why did not God just say, “I forgive you,” and let it go at that?Read more at http://dogmatics.wordpress.com/2014/11/25/costly-love-an-analogy-of-the-atonement/
We can catch a glimpse of the answer with an analogy in human relationships. Suppose I have done something that deeply hurts a friend, and he says so me, “That’s OK. It doesn’t make any difference. Forget it.” Has he forgiven me? What he has really said is: “I don’t really care enough about you to be touched by anything you say or do. You are not that important to me.” Not only that; he leaves me alone with the awareness of my guilt. He lets me “stew in my own juice,” refusing to help me by letting me know that he suffers not only because of what I have done to him but because he knows how I feel and can share with me my shame and guilt.
Good-natured indulgence and broad-mindedness, in other words, are not forgiveness and love but indifference and sometimes even hostility. Real love and forgiveness mean caring enough to be hurt, caring enough to put oneself in the other’s shoes and sharing his guilt as if it were one’s own. Real love and forgiveness are costly — not in the sense that the guilty must squeeze them out of the injured, but in the sense that the injured freely participates in a guilt not his own.
[Christian Doctrine (Richmond, VA: CLC Press, 1968), 253. It is currently published in the revised 1994 edition from WJK Press.]