When you buy the physical disc based version of a PC game, one would think you'd get to skip the part where you download thousands upon thousands of megabytes before you can start playing. Not the case for Metal Gear Solid V: The Phantom Pain.
At least according to Twitter user graphμre | グラフ, who thankfully has provided evidence, the disc based retail version of Metal Gear Solid V: The Phantom Pain for PC, doesn't include any of the game files. All you get is the code for the game, and an 8,78 MB installer for the Steam client.
This leaves you with downloading the game as the only option, effectively making the box version you bought just that. A box.