Sorry that this refers to something so far back as Ch.12, but I'm taking the GR guideline that says "feel free to make references back to chapters we have already read" at face value!

I've just caught up with the note in the Norton edition that says with regard to Willoughby's intended present of a horse to Marianne:

According to John Trusler, a domestic economist of the time, the cost of feeding and maintaining horses doubled during the Napoleonic Wars, rising to about £40 per year, which would be a huge portion of Mrs. Dashwood's annual budget.

This gives a bit more perspective to the discussion on this board, both about Willoughby's thoughtlessness in making this offer and Marianne's in accepting it.