Singing on 'American Idol' is apparently good for the bank account ... even if you're already a superstar.

After their performances on the show's Grand Ole Opry week, Brad Paisley, Carrie Underwood and Randy Travis all saw huge spikes in sales of CDs and singles. According to Music Row Magazine, Underwood and Travis' duet, 'I Told You So,' had sales of more than 100,000 downloads the week after they performed it together on the show, making it the week's No. 8 biggest-selling single. Underwood's solo version of the song also saw sales jump by 24%, and her sophomore album, 'Carnival Ride,' went up an impressive 59% in sales.

Travis' latest album release coincided with his appearance on 'Idol.' 'I Told You So: The Ultimate Hits of Randy Travis' made its debut on the country charts at No. 3 with sales of more than 16,000 units. Similarly, Paisley debuted his new single, 'Then,' on the show. It quickly sold more than 64,000 units, making it the No. 18 biggest-selling single of the week.