One theme of this text is that people are willing to make sacrifices for those that they love. These sacrifices make the love more meaningful. Della sacrificed her dignity and pride all year by "bulldozing (haggling with) the grocer and the vegetable man and the butcher," so that her "cheeks burned"; she knew they must realize how poor her family is. The reason Della went through this demoralizing experience was to save money and buy her husband, Jim, a beautiful Christmas present. It is important to her to purchase something "fine and rare and sterling" because she wants to buy a gift "just a little near to being worthy of the honor of being owned by Jim." She loves her husband so much that she is willing to embarrass herself all year to save pennies to spend on a gift for him.
Della looks in the mirror and she has the idea to sell her beautiful hair, though it is her most prized possession. When she goes to Madame Sofronie's shop and hears her offer of $20, Della says "Give it to me quick." She is afraid of backing out before it is done unless she is holding the money. Despite how much she loves her beautiful hair, she is willing to sacrifice it to buy Jim a lovely watch chain because she loves him so very much.
When Jim gets home, Della is so excited to give him his gift. However, he gives her the gift he procured for her first and confesses that he "sold [his] watch to get the money to buy [her] combs." She admired a beautiful set of hair combs in the past, and Jim sacrificed his most cherished possession for Della just as she has sacrificed hers for him. He isn't upset, of course, because he realizes they did the same thing: made a personal sacrifice for the one they love. This makes their love all the more special.