One example of humor Jane Austen uses in Pride and Prejudice to expose the ridiculousness of the search for marriage can be seen in the opening scene. In this scene Mrs. Bennet is trying to persuade Mr. Bennet to visit and introduce the family to Mr. Bingley who has just purchased the Netherfield estate. The conversation is particularly amusing because Mr. Bennet teases his wife about her interest in Bingley for their daughters. In particular, Mr. Bennet asks how Bingley's taking Netherfield could affect the girls and when Mrs. Bennet asserts that Bingley might fall in love with one of them, Mr. Bennet replies that he sees no reason to visit Bingley, but Mrs. Bennet and the girls can go, which of course, would be a social faux pas.
A second example is seen when Mrs. Bennet learns that Wickham has successfully been forced into marrying Lydia. Rightfully, when Mrs. Bennet first learns that Lydia has run off with Wickham, she bemoans the fate of Lydia's reputation and the rest of her family's reputation. However, when she learns Lydia will be married, all thoughts of Lydia's wrong-doing fly right out the window. Instead, Mrs. Bennet is jubilant that she finally has one daughter married and demands Jane and Elizabeth to ask Mr. Bennet how much money he will give Lydia for the wedding clothes. The humor in that scene is the irony in her sudden change of behavior when the circumstances haven't changed at all.