In Chapter 11, Equiano uses verbal irony to highlight the injustice of the way Black laborers are treated in all sectors of the global economy:
One day I went with a free negro tailer, named Joe Diamond, to one Mr. Cochran, who was indebted to him some trifling sum; and the man, not being able to get his money, began to murmur. The other immediately took a horse-whip to pay him with it: but by the help of a good pair of heels, the tailor got off.
Mr. Cochran owes Joe Diamond money in exchange for his services. As Equiano writes, it is "some trifling sum"—in other words, not very much money at all. Instead of paying Diamond this "trifling sum," Mr. Cochran threatens to beat him with a whip. Equiano's phrasing is ironic: he states that Mr. Cochran gets out the whip "to pay [Diamond] with it." Obviously, beating someone is about as far as a person can get from paying them in valuable currency. Equiano trusts his readers, largely wealthy white men, to recognize this as a slimy business deal and feel affronted that a merchant would ever be treated this way. Even if the money itself is negligible, someone who renders a service should be paid fairly. Threatening physical violence against a merchant for requesting due compensation is dishonorable and violates the core tenets of capitalism and free trade.
And yet, on some level, Equiano is also being literal. Enslaved Black laborers around the world are regularly compensated for their work with physical and mental abuse. Joe Diamond is a free laborer who is trying to participate in the free market economy, and yet his Blackness makes Mr. Cochran feel insulted at the very idea that Diamond would expect money (as any white laborer would) in exchange for his services. Equiano uses verbal irony to demonstrate that slavery and its racist logic is corrupting the "free market," making it less free.