You're missing the point here, no one is comparing the two as if a country's GDP represents something equivalent to the value of a company. They're just saying

You're missing the point here, no one is comparing the two as if a country's GDP represents something equivalent to the value of a company. They're just saying something along the lines of "Wow! 3,000,000 gallons of water?!? That's more than the amount of water that flows past my house on the river in a year!" (Obviously made up numbers)