Had the Queen of Sheba lived in the flat across the air shaft, Della would have let her hair hang out the window someday to dry, just to depreciate Her Majesty's jewels and gifts.  Had King Solomon been the janitor, with all his treasures piled up in the basement, Jim would have pulled out his watch every time he passed, just to see him pluck at his beard with envy.

In this passage of the exposition of "The Gift of the Magi," O. Henry alerts the reader to the pride and wealth of the Dillinghams.  That their possessions are superior to those of the Biblical allusions also gives them a magnitude beyond the ordinary.  Yet, as beautiful and valuable as these two possessions are, Jim and Della value their love for each other far more and are, thus, willing--even happy--to sacrifice for the other these valuables in which they take personal pride.

In a final Biblical allusion, O. Henry makes another comparison:  that of Jim and Della to the Magi, who were wise.  But, O. Henry declares,

Of all who give and receive gifts, such as they are wisest.  Everywhere they are wisest.  They are the Magi.

Jim and Della purchase gifts to accompany and exhibit the most valued possession each owns.  "Foolishly," as O. Henry writes, they ironically lose their own valued possession in the process of procuring their gifts.  Still, they are "wise" because JIm and Della realize that love is both the greatest gift and the most valuable gift.  For this reason they are the "wisest."