[IggleSniggle]

Yes, exactly!

And since "important" is relative to the person making the sacrifice, it's easy for a person to declare something a sacrifice when what they were giving up was not especially important to them, or on the other hand for someone to dismiss a "real sacrifice" that someone else has made as unimportant.

Not that this matters, really. But I think it's important not to use them synonymously. In the case of an opportunity cost, you are acknowledging that there were things given up. In the case of a sacrifice, you are saying there were things given up _and it hurt_.