Or, in another example, one often hears parents talk about how they "sacrificed" to give their children a good education.

Strictly speaking, this is nonsense. They've sacrificed nothing at all. When facing the daily choices of spending more money now and enjoying a higher standard of living, or saving the money to ultimately provide a higher education for their children, they voluntarily chose to save the money, choosing what was for them the higher value of an education for their children.

Others, when faced with exactly the same choice, have chosen to spend the money. Each family "sacrificed" nothing, merely making voluntary choices based upon what it viewed as a higher value at the time.

If then, an individual voluntarily presents him or her self to be killed on an altar before some deity, certain that some greater benefit will accrue to him or her self in the after life, or to the clan or tribe, has a "sacrifice" occurred?

Clearly, we can see that, if the act was wholly voluntary with the belief of some greater value to be gained, it has not. Indeed, to the individual concerned, it was believed to be a profitable exchange.

In most such cases, however, those to be sacrificed in such a manner, or those whose property was chosen to be the sacrifice, were selected by priestly designation or edict, or through some sort of random lottery (certainly an indication of an absence of willing and eager volunteers!)