My edition was edited by Vivian Jones and contains notes from Chapter 4 that references The Jane Austen Handbook edited by J David Grey and the English Landed Society of the Eighteenth Century,GE Mingay..

In the General Notes about Social Class says that the term "'pseudo-gentry' is used to describe a group comprising trade and professions who aspired to the lifestyle of the traditional rural gentry and whose growing fortunes often meant that they could afford to buy into it by aquiring property--as the Bingleys are seeking to do at the beginning of the novel"..

The Bingleys aquired wealth would put them in 3rd class in terms of graditions of rank and fortune--behind 1st the nobility of the land and 2nd the old families of wealth and consequence;(Clare Reeve's Plans of Education, 1792)

From the Notes For Chapter IV:
For the notes on "very fine ladies": "the Bingleys are very wealthy. The Bingley sisters' independent fortunes of 20,000 would yield a disposable income of 1,000 a year (in comparison with the Bennet sisters' 1,000 capital) Bingley's income of 'nearly 100,000' would yeild 5,000 per year, an income comparable with those in Mingay's category of 'wealthy gentry'. But this money has been made in trade and the Bingleys are looking to consolidate their fortune and secure respectability by buying into land."