Marriage in Jane Austen’s time.

            In time of Jane Austen, woman could not be independent. Professions were not open to women. Few occupations were open to them, and those were not highly respected, they did not earn enough money or the working conditions were not good. Only a few number of women though their own efforts earned an income sufficient to make them independent, or had a recognized career. (Jane Austen was not one of these few women professionals).

            Most graceful women could not get money unless she decides to marriage. A woman could only be a "heiress" if she had no brothers. Unmarried women had to live with their families, or with family-approved protectors. Therefore, a woman who did not marry had to live with her relatives as a `dependent' (more or less Jane Austen's situation), so marriage is the only way of getting out from under the parental roof; unless, her family could not support her, in which case she could face the unpleasant necessity of going to live with employers as a `dependent' governess or teacher, or hired "lady's companion

            When a young woman left her family without their approval, this spawned an enormous problem, such as running away to marry a disapproved husband, or entering into an illicit relationship. Because all this reasons, some women were willing to marry just because of the fact that it was the only allowed route to economic security and a better quality of life.

            In Pride and Prejudice, this theme is expressed by the character of Charlotte Lucas: "Without thinking highly either of men or of matrimony, marriage had always been her object; it was the only honourable provision for well-educated young women of small fortune, and however uncertain of giving happiness, must be their pleasantest preservative from want." She is 27, not especially beautiful (according to her and Mrs. Bennet), and without an especially large "portion", and so decides to marry Mr. Collins "from the pure and disinterested desire of an establishment".

            According to Mr. Collins: "This young gentleman [Darcy] is blessed with everything the heart of mortal can most desire, -- splendid property, noble kindred, and extensive patronage". Mrs. Bennet's on Elizabeth's marriage exclaims: "What pin-money, what jewels, what carriages you will have! ... A house in town! ... Ten thousand a year! ... I shall go distracted!"

              Jane Austen expresses her opinion clearly enough by the fact that only her silliest characters have such sentiments.

Source: http://www.pemberley.com/janeinfo/pptopic2.html