What is the theme of the story The gift of the Magi written by O. Henry?

Another theme is the material value
or materialism. Here these folks are economically stretched. When
they each give up an item for the other, it happens to be the most important item or
object in the world to them. This shows that their relationship is of more value than
things which is a strong point O. Henry is trying to
make.

On the flip side, as each receive an item from each
other because the items required to use the new gifts are gone, they have absolutely no
value. So now, rather than them both having something they value, what they have
materially is worthless and all they are left with is their relationship. This may not
be such a bad deal after all.