My copy has an introduction that talks about how this book, and indeed, all of JA's novels, can be said to be studies in knowledge. Who knows what and when, whose knowledge is suspect, what are the effects of knowing too much or not enough.

This read, I paid more attention to the 'rewards' the characters get. As others have noted, Lucy and Robert do come out 'ahead' of Elinor and Edward in material things--but maybe not in real happiness.
"What Edward had done to forfeit the right of eldest son, might have puzzled many people to find out; and what Robert had done to succeed to it, might have puzzled them still more. It was an arrangement, however, justified in its effects, if not in its cause; for nothing ever appeared in Robert's style of living, or of talking, to give a suspicion of his regretting the extent of his income, as either leaving his brother too little, or bringing himself too much; -- and if Edward might be judged from the ready discharge of his duties in every particular, from an increasing attachment to his wife and his home, and from the regular cheefulness of his spirits, he might be supposed no less contented with his lot, no less free from every wish of an exchange."