In the play A Doll's House, by Henrik Ibsen, we find as main characters the married couple made of Nora and Torvald. We know that Nora is less of a wife and more like Torvald's play thing. Meanwhile Torvald takes seriously his role as a head of household and provider to the family.These different roles make it hard for Nora and Torvald to agree in anything remotely connected with money.
Nora is a true spendthrift. However, the reason why she spends so much money is that, for the first time, she feels free from the constraints that she once went through trying to get money to take care of Torvald during his illness. She also suffers consistently because the man who loaned her the money to take care of Torvald, Krogstad, is now blackmailing her. Hence, Nora's desperation for money has always been so that she can pay off Krogstad and be left alone.
Now that Torvald will be promoted at his job, Nora feels that she will be financially free to enjoy her life. This is not Torvald's view, however, because he is more conscious about finances, and always plays it safe. Yet, it is also arguable that Nora simply knows that Torvald will weaken down and give her everything and anything she wants because that is precisely her job: To entertain him with her little spoiled girl antics.
Therefore, money is a unifying element in the marriage of Nora and Torvald, but it will also serve as the reason behind their separation.