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"She's not leaving me!" Tom's words suddenly leaned down over Gatsby. "Certainly not for a common swindler who'd have to steal the ring he put on her finger."
"I won't stand this!" cried Daisy. "Oh, please let's get out." (7.275-281)
And one last proof that Tom sees marriage as an economic exchange: he's "bought" Daisy honestly, but Gatsby would have to buy her dishonestly. No word on what Daisy wants, of course.