"Magi" has to come to imply "wise men". What is ironic in the title "Gifts of the Magi" by O. Henry?

Rather than being ironic, the argument can be made that the title "The Gift of the Magi" is metaphoric. For, in the conclusion of the story, O.Henry, intrudes as narrator,

The Magi, as you know, were wise men--....They invented the art of giving Christmas presents. Being wise, their gifts were no doubt wise ones....And here I have lamely related to you the uneventful chronicle of two foolish children in a flat who most unwisely sacrificed for each other the greatest treasures of their house.  But in a last word to the wise of these days, let it be said that of all who give gifts these two were the wisest.  Of all who give and receive gifts, such as they are wisest.

O. Henry clearly states overtly his theme that the "foolish" love of Della and Jim is really the truest love and overtly states also that Jim and Della are the magi and they are "the wisest."  While the reader initially recognizes the Biblical allusion of the title, as he/she reads, the reader then realizes that the title is a metaphor for Jim and Della, ironically stated, perhaps, since the "foolish" children are "wise."  Typical of his endings, O. Henry sets on end coventional ideas in "The Gift of the Magi."