The speaker tells someone she loves that their careless words hit like whips from Hell. That admission sounds grim, but she quickly twists it: if pain is unavoidable, at least it gives her songs to sell. The people who wound her become “profitable Friends” because they supply material for poetry. That mix of bitterness and shrewdness is the whole mood of the poem — wounded but not helpless, almost mocking the people who hurt her.
The title “The Economist” points to this same idea. The speaker treats emotional suffering as an economy: love brings pain, pain becomes art, and art brings profit. Her farewell is not tender. It sounds cool, proud, and a little defiant, as if she is settling accounts and leaving with the only thing of value she can take from the relationship.