Through the sacrifices Della and jim make for one another, they prove love is more important than material possessions. as the narrator says "of all who receive gifts, such as they are the wisest." When they make such sacrifices, they do it to make the spouse happy. They sell their most prized posession for each other. For jim, it is a family heirloom, his grandfather's watch, and for Della, its her long, beautiful hair.
"She got out her curling irons and lighted the gas and went to work repairing the ravages made by generosity added to love. Which is always a tremendous task, dear friends—a mammoth task."
“Jim, darling,” she cried, “don’t look at me that way. I had my hair cut off and sold because I couldn’t have lived through Christmas without giving you a present. . . . Say ‘Merry Christmas!’ Jim, and let’s be happy. You don’t know what a nice—what a beautiful, nice gift I’ve got for you.”
"Many a happy hour she had spent planning for something nice for him."
"Maybe the hairs of my head were numbered,” she went on with sudden serious sweetness, “but nobody could ever count my love for you. Shall I put the chops on, Jim?"