Former Enron bosses Kenneth Lay and Jeffrey Skilling stole from investors both to line their pockets and stroke their egos, their trial has heard.
The comments came from prosecutors presenting their closing arguments at the court in Houston, Texas.
Prosecuting lawyer Kathy Ruemmler said the case centred around “the lies these men told and the choices they made”.
Ms Ruemmler told the court on Monday that for both men “Enron was their ego”.
“Make no mistake,” she said. “There is absolutely nothing wrong with getting rich but you can’t get rich by deception, by cheating.”
The defence will make its closing arguments on Tuesday, and the jury is expected to begin its deliberations on Wednesday.
Mr Skilling, 52, Enron’s one-time chief executive, faces 28 counts of fraud and conspiracy.
Mr Lay, 64, the firm’s founder and former chairman, is charged with six such offences.
Both could be sentenced to more than 30 years in jail if convicted.