These many demons she has to face up to are rutheless in their demands. The wager suggested refers to this — it originates from Shakespeare’s Merchant of Venice. The insistence by Shylock of the payment of Antonio’s flesh is the central plot device of the play.
In an interview with Chelsea Handler, Florence talks about how song-writing is exorcising the “demons of the night before”, and the “pound of flesh” reference is the offering of a song to the demon.
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