$2 each from Nintendo's eShop.
The sale discounts the Wii U Virtual Console version of Mega Man X (regularly $7.99) and the 3DS VC port of the Game Boy Mega Man (regularly $3.99). Note that these limited-time sale prices are only available via their respective platforms, as Nintendo does not offer the ability to purchase eShop content via PCs.
This week's sale is apparently the first of several "2 Games, 2 Dollars each, 2 Days" deals planned for the eShop, though details regarding future sales have not been revealed. The sale price for both games will remain in effect through 8:59 a.m. PST on December 18.