Natalie Tyler, "A Fling at the Salve Trade" gives an interesting explanation. She cites the following from the text:

"Miss Hawkins was the youngest of the two daughters of a Bristol -- merchant, of course, he must be called; but, as the whole of the profits of his mercantile life appeared so very moderate, it was not unfair to guess the dignity of his line of trade had been very moderate also. Part of every winter she had been used to spend in Bath; but Bristol was her home, the very heart of Bristol...And all the grandeur of the connection seemed dependent on the elder sister, who was very well married, to a gentleman in a great way, near Bristol, who kept two carriages!"

She says: Mr. Hawkins, who has settled a full ten-thousand pounds on his younger daughter is no ordinary merchant; the richest merchants were making an average annual income of only twenty-six hundred pounds per annum in 1803. How could the family have become so wealthy? The above paragraph fairly drips with sarcasm and innuendo: "merchant, of course, he must be called," "as the whole of the profits of his mercantile life appeared so very moderate, it was not unfair to guess the dignity of his line of trade had been very moderate too." Bristol is mentioned four times in a relatively short passage, and Mrs. Elton comes from the "very heart of Bristol." Could that be a "heart of darkness," in a Conradian sense of a place where people take advantage of people weaker than themselves? The clincher is the name Hawkins. Sir John Hawkins had introduced the slave trade to England. Austen does not write in polemics. Her devastating portrait of Mrs. Elton as a parvenu, a ruthless narcissistic arriviste who is cruel to (spoiler) and infuriatingly complacent about her role as lady patroness of Highbury, is, her implicit condemnation of those who are indifferent to the trade in human flesh.