Amazon offers its Prime members X-Men: Days of Future Past on Blu-ray Disc for $9.99 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, it adds $4.98.) That's the lowest total price we could find by $10.

Also available for Prime members is X-Men: Days of Future Past on DVD for $9.99 with free shipping. (SimplePleasures777g via eBay offers it for pennies more.) That's the lowest total price we could find by $4.