In Act 1 Scene 6, lines 25-28, Lady Macbeth uses the words 'compt', meaning account, and 'audit', meaning financial report.
What is the point that she is trying to get across to Duncan by using this financial imagery?
Lady Macbeth is already planning the murder of Duncan by Act 1 Scene 6. The extended financial metaphor would, on the surface, be a way of interacting in a witty but respectful way with her esteemed guest, the King. However, as we also appreciate the duplicity of Lady Macbeth, and her vile motives, it is possible that her words also have a more sinister suggestion.
My interpretation would be that Lady Macbeth is considering the ideas of ’worth’ and ‘value’. Her husband has risked his life for his monarch, and will be financially rewarded for his efforts, but she sees a greater value in the power that he could be afforded had he dispatched the king himself, rather than his enemies. As the witches’ prophesy adds weight to her contemplations, by Act 1 Scene 6 she is considering the debt that her husband is owed, and how Duncan should pay with his life, rather than his gold.