As the title indicates, one of the chief contrasts in the book is between the overly sensible and emotionally controlled Elinor and the sentimental drama queen Marianne. Their different temperaments are used to draw ironic contrasts between how the two view life.
Marianne is described as similar to Elinor except that she is:
eager in everything: her sorrows, her joys, could have no moderation. She was generous, amiable, interesting: she was everything but prudent.
Marianne's tempestuous way of throwing herself whole-heartedly into every emotion she is feeling at the moment causes her to condemn her sister for not falling immediately into the throes of love with Edward. When Elinor sensibly won't say she is head over heels in love with him, Marianne berates her:
Esteem him! Like him! Cold-hearted Elinor! Oh! worse than cold-hearted! Ashamed of being otherwise. Use those words again, and I will leave the room this moment.
The irony in Marianne's statement is that Elinor is not being cold hearted—except for by Marianne's dramatic standards.
In a novel that profoundly recons with how our point-of-view impacts our judgments, Austen plays with Elinor's and Marianne's conflicting perspectives on what is a humble income to scrape by on. Marianne, in Romantic fashion, says she needs very little to live on. Elinor doesn't believe it, and she asks her to name a minimum figure. Ironically, Marianne's minimum is twice Elinor's idea of wealth:
"Perhaps," said Elinor, smiling, "we may come to the same point. YOUR competence and MY wealth are very much alike, I dare say; and without them, as the world goes now, we shall both agree that every kind of external comfort must be wanting. Your ideas are only more noble than mine. Come, what is your competence?"
"About eighteen hundred or two thousand a year; not more than THAT."
Elinor laughed. "TWO thousand a year! ONE is my wealth! I guessed how it would end."
In a famous scene early in the novel, readers learn that the girls's dying father asked his son, John Dashwood, to take care of his widow and daughters. The father's idea of adequate provision is far removed from what John and his selfish wife Fanny decide is enough for the women. It is a cruel irony that Mrs. Dashwood and her daughters end up with far less than their husband and father would have left them if he had made provisions in a will.
Finally, it is good to keep in mind while weighing contrasts that the story is told from Elinor's point of view. She is unaware until late in the novel that she suppresses her feelings too much. She has missed out on the warmth and comfort her sister could have provided, but she was overly self controlled. Ironically, the novel, at least in the beginning, satirizes the overly emotional sister.