Don't you just love when someone gives you a gift for no reason other than that they love you?
I love getting a gift. It means that someone was thinking of me, someone cares for me, and someone was willing to give up something (money, time) to get it for me.
Your response is usually humble joy to realize what the person has done for you.
God has given us an indescribable gift. He loves us, He thinks about us and His gift to us cost Him the very life of His only son! That is a pretty huge price tag.