The 39-year-old actress first introduced the character of forensics expert Sara Sidle in 2000.
She is quitting the show in November after failing to agree terms on a new deal.
In an exclusive chat with TV Guide magazine, Fox reveals, "A couple of years ago, I decided not to take the raise that was offered me, (which) would have added a year to my contract."
The actress admits she still feels frustrated and hurt after CSI producers fired her and costar George Eads following a salary dispute in 2004.
She adds, "I wasn't sure I wanted to give anybody any extra time. And the raise was terrible, to be frank. An extra year for that amount of money? No, thank you."
But the actress admits she'll miss her onscreen love interest, William Petersen: "He's the most incredible scene partner I've ever had and he's a great friend. I couldn't have scored any higher than getting William Petersen to be my boyfriend on TV."
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