How well off do we imagine the Dashwood women are following their removal to Barton? Obviously even with Elinor economising they're not going to be building extensions! FD seems to think (or at least she persuades her husband to think!) that they will be able to live extremely comfortably without their giving them anything further. At this point they are assuming a house in the neighbourhood will be rented and this would presumably be at a greater cost that Barton Cottage which they have on Very Easy Terms.