Consent, or at least not active opposition, is thought (I BELIEVE) to be a reason for sacrificed humans to be drugged in some way. Get them so high they're happy when they go, kind of thing.

Is Abraham a good parallel? It's not his life on the line there. Did Isaac volunteer?

[ETA: And it shows up in Iphigeneia, too...]

The idea recently turned up in The Vikings when the family go to the big shindig at Uppsala and it turns out that Ragnar Lothbrok had pledged a sacrifice who wasn't actually willing to do it.