The Pretty Woman actress starred as the wife of George Clooney's character Danny Ocean in the 2001 heist film and agreed to appear for a fraction of her usual fee.
And it was a funny letter containing a $20 (£12.50) bill from Weintraub, Clooney and director Steven Soderbergh that won her over.
In his upcoming memoir, Weintraub reveals the note read: "We know you get 20 (million dollars) for a movie, but you will have to work for a little less on this one."