Sentence:  If you exchange a penny for a dollar, it is not a <WSD>sacrifice</WSD>; if you exchange a dollar for a penny, it is. 
Meaning of the word marked with <WSD> tags:  To trade (a value of higher worth) for something of lesser worth in order to gain something else valued more, such as an ally or business relationship, or to avoid an even greater loss; to sell without profit to gain something other than money.