In the “Gift of the Magi” by O. Henry, both Della and Jim make sacrifices. A quick assessment might say that these sacrifices were superficial. After all, Della cut off her long, beautiful hair to buy Jim a watch fob, and Jim sold his watch to by Della combs for her hair. Not a huge sacrifice since hair grows back, and one can always buy another watch—right? Let’s look at what these items represent. Della sacrificed one of her most attractive features as a woman. Hair is equated with femininity, so by cutting it short, she sacrificed some of her feminine identity. Jim sacrificed a piece of his family history. No watch can ever replace what his symbolically represented. Fortunately, they realized that these aspects were secondary to the love that inspired the sacrifice.
Enotes has some good resources.