The Bingley sisters represent two central themes found in Pride and Prejudice. The first theme concerns consequences of prejudice. However, the Bingleys' prejudice stems from, not just their own character flaws, but a social phenomenon occurring within Jane Austen's time period. During this time, the merchant class, or working class, was becoming increasingly wealthier, wealthy enough to purchase their own estates and rub shoulders with the well-established landed gentry. The new wealthy merchant class established a brand new class, the middle class. The Bingley sisters were actually a part of this new wealthy merchant class; however, the fact that they were now rubbing shoulders with the upper class elite has made them look down there noses upon everyone else in society, even those who are still members of the working class. Hence, another theme the Bingley sisters represent concerns the moral implications of class distinctions.
From the very beginning of the book, Austen uses the character traits of the Bingley sisters to illustrate her theme of prejudice. When we first meet the Bingley sisters, Austen describes them as "proud and conceited" and as believing themselves to be "entitled to think well of themselves, and meanly of others" (Ch. 4). Later, we see them being very snobbish and critical. When they invite Jane over to dine with them at Netherfield, they later laugh behind her back about her relations, such as her uncle that is a lawyer in Meryton and her uncle that is a merchant residing in Cheapside. They even treat Jane very poorly. When Jane is in London with the Gardiners, Miss Bingley eventually returns Jane's call, but Miss Bingley makes it very clear that "she had no pleasure" in seeing Jane, so much so that Jane became resolved to end the friendship (Vol. 2, Ch. 26). All of their poor behavior is a result of their judgement of people they deem as beneath them. Since Jane comes from working class relations, out of prejudice, they treat her very poorly, which helps to portray Austen's theme of prejudice.
However, the irony is that the Bingleys actually come from the working class themselves. We learn when we first meet them that the Bingley fortune was earned through trade. Hence, Austen is also using the Bingley sisters to point out the consequences of class distinctions. All throughout the book, Austen mixes classes, showing us that she sees no value in class distinctions. One example of mixing classes is seen when Elizabeth, a gentleman's daughter with working class relations, marries Mr. Darcy, a gentleman with noble, upper class relations like Lady Catherine de Bourgh. Thus the fact that the Bingley sisters come from the working class themselves but are now looking down there noses at the working class shows us that Austen is using them to make a point about class distinctions. She moralizes that class distinctions are wrong, resulting in poor, cruel, and prejudicial treatment. Hence, Austen also uses the Bingley sisters to illustrate her theme concerning the moral implications of class distinctions.