There is a new book out on slavery, The Making of New World Slavery by Robin Blackburn, and there is an excellent review of it in this week's Times Literary Supplement, "The children of Ham" by Anthony Pagden. It sheds some rather unpretty lights on Mary Crawford's difficulties in getting her harp set up Mansfield Park, Chapman I:6, 57-9)
Pagden says that Blackburn's book brings home the important point that slavery of the 17th through 19th centuries provided the pomp, the "superabundance and concern with display" that characterized the upper class life in parts of Europe. Pagden quotes Diderot to this effect: "modern slavery, wrote an indignant Diderot, in 1780, 'is a trade which is based upon injustice and has only luxury as its object'" (TLS, p 4). Hill and Wimpole Streets would then be the urban version of the Arcadian pomp of Mansfield Park and Sotherton, all of it the result of the agonies of slaves. Repton's job was the result of the slave market, so too Henry Crawford's supposed "capability." And so too Mary's heavy harp--a harp such as Mary plays as she sits near the green world in her elegant clothes in Mrs Grant's front room may be seen as an emblem of wealth (Mansfield Park Chapman I:7, 65). Harps were expensive, symbols of conspicuous consummation. The Prices may be compared to those in our world who have a tiny seat at the back of the bandwagon, get the crumbs which fall from the pursuit of empire.
In this light Mrs Norris's sponging is a more petty example of living off the wealth garnered--Austen says she had a genuine "ill-will" against Fanny because she treated her so badly; I'd like to remark here she is also a female dependent upon Sir Thomas's largess (the Moor Park is paid for by Sir Thomas, genuine or not), and she may also be motivated by a desire to make sure no-one will see she is not so different in status or power from her despised niece. She is very jealous of Fanny, and if we may say she brought Fanny there and provided Fanny with all the good things she ends up with she regrets it; she ends hating Fanny and blaming Fanny for Maria's downfall when we know who was the false mother here.