Amazon offers Prime members Nightwish: Showtime, Storytime on Blu-ray / CD for $12.49 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, it adds $3.98.) That's the lowest total price we could find by $18. Included are two CDs and two Blu-Ray discs, including live show footage and a 2-hour documentary.
Note that this item is in stock but may take an extra day or two to process.