I am not saying that Mr. Bennet and/or Lizzy always speak for Austen. I think this passage would have been as significant were any other character to utter the "unhappy alternative" sentences. Of course, since they are meant to be somewhat humorous, only Mr. Bennet could have uttered them and remained in character. But his words only serve to highlight a plot point. Mrs. Bennet was the one who said she would no longer speak to Lizzy, if she did not marry Mr. Collins. Mr. Bennet was responding to that, and to the proposal itself. I think it is a mistake to view this passage as just another of Mr. Bennet's sardanic quips with no further meaning. Was Austen just trying to get us to laugh, or was something deeper going on?

I think no one would argue that Mrs. Bennet's view of marriage is Jane Austen's. Nor would any Pemberlean argue that Lizzy made a mistake in rejecting Mr. Collins. If Lizzy's choice is truly between the views represented by her 2 parents, that leaves only Mr. Bennet's.