In "The Gift of the Magi," O. Henry most likely uses the irony of the couple’s gifts to express the theme that

Della sells her hair to buy Jim a chain for his prized watch, while Jim sells his watch to buy combs for Della’s hair. Their gifts become unusable because each has sacrificed the very possession the other’s gift was meant for. This irony shows that their willingness to give up what they treasure for each other matters more than the gifts themselves, expressing the virtue of love and sacrifice.

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