What incident contrasts her values with her husband values?

The invitation to the party contrasts their values. Mr. Loisel expects his wife to be thrilled at the invitation he procured for her. She, on the other hand, carries on like it's the worst thing that has ever happened to her. Mr. Loisel cherishes the small things and appreciates them to their fullest. His wife, however, always wants more. Nothing is ever good enough.