I don't share your point that sacrifice implies a finality of what is sacrificed. Like money, for example, can be sacrificed and regained. Surely some things are irreplaceable but not all things.

His sacrifice was His life. It is to be accepted that He gave Himself, being one who did everything right and nothing wrong, in the place of those who didn't and did, to take the consequence of the offences on behalf of the offenders. He did this by volunteerily limiting Himself to the abilities of a common man. If He would not of restrained Himself as so, yeah, I'd agree with you, it would have been no big deal. But as the story goes, He did die a human's death and was risen as a human. Whether you or I believe it doesn't change that He sacrificed His human life. If you're interested maybe read Philippians chapter 2 or The Gospel of John.