Quote 82
Thirdly, […] the nation's stock will be thereby increased fifty thousand pounds per annum […] and money will circulate among ourselves, the goods being entirely of our own growth and manufacture. (22)
Swift raises an interesting point: are children the only "goods" entirely owned by Irish peasants, since they can't lay claim to their own land?
Quote 83
Many other advantages might be enumerated: for instance, the addition of some thousand carcasses in our exportation of barreled beef; the propagation of swine's flesh (26)
It doesn't look like the wealthy differentiate between types of meat. Beef, swine, child—all are precious commodities in A Modest Proposal.
Quote 84
Supposing that one thousand families in this city would be constant customers for infants' flesh (27)
Since the narrator has already estimated the number of children for sale, it stands to reason that he would estimate the number of greedy families. Notice the relatively small number of wealthy families (1,000) compared to children designated for food (120,000).