This is THE cheapest price for the 360 version Metal Gear Solid V: The Phantom Pain… and possibly for all platforms.
Do note it's 6.63GB in size and does not include the 'Day One' DLC, which is usually included in every physical copy of the game. The DLC itself is just a bundle of cosmetic weapons and cardboard boxes.
And pants.
FYI Xbox One version is $39.95