How can something be called a sacrifice when nothing has really been lost?

While reading through a discussion thread on another website, I came across a comment that brought to light a couple of important questions about this whole "Jesus died for me" belief. The comment basically stated that Jesus is believed by xians to be a god who couldn’t really die or even sin and is apparently alive and well. The commentor pointed out how xians weep with sorrow when they hear the story about Jesus' death for the millionth time even though they believe their savior lives. One minute they are crying and feeling sad..."Terrible how sinners killed Jesus...boo hoo" and then "He lives! He lives! Hallelujah!" the next.

Webster dictionary defines sacrifice as "a: destruction or surrender of something for the sake of something else b : something given up or lost". So, the question remains "How was Jesus' death a sacrifice?" How can something be called a sacrifice when nothing has really been lost?