Guncrafter Industries is a custom handgun company formed by one Alex Zimmerman in 2002 after many years working for Wilson Combat. Among other things, they make custom 1911 pistols chambered for the .50 GI (Guncrafter Industries) cartridge, also designed by Zimmerman. The idea of the cartridge is to have a larger bullet diameter without having the excessive power and recoil of a magnum type round like the .50 Action Express or .45 Winchester Magnum. The .50GI is loaded to .45 ACP pressure levels, and offers loadings ranging from 185gr @ 1200fps to 300gr @ 700 fps. The case head is rebated, and the same size as the .45ACP case head, allowing for easy conversion back to .45 ACP if one desires.
The basic conceit of this pistol and cartridge is that a larger bullet is more effective and thus worth the less of capacity (.50GI magazines hold 7 rounds). Whether that actually stands up to reality does not seem assured, especially considering the vast amount of development which has gone into smaller caliber expanding bullets compared to the few basic offerings for the .50 caliber.
Of course, it’s also possible that the gun is just simply based on the giggle factor of having a fifty caliber 1911.