It also gives some perspective to the following statement about Willoughby in Ch.14 :-

His estate had been rated by Sir John at about six or seven hundred a year; but he lived at an expense to which that income could hardly be equal, and he had himself often complained of his poverty.

It is hardly surprising Willoughby is broke if you think how many horses he has - two for the curricle, at least one hunter, the brown mare he's trying to flog to Col. Brandon, and Queen Mab who he wanted to palm off on Marianne and Mrs D. At a conservative estimate that's nearly a third of his income gone on horses alone, not to mention the cost of a groom.