under any regular development it's impossible to get to that number.
However there have been cases where developers got into trouble with not having enough variables due to specific design decisions (bad decisions in my opinion, but that is beside the point).
For example there was one person who decided to use variables to get every actor assigned with new skill values and new parameter values, because with variable he could do whatever he wanted.
And then he ended up with twenty variables needed for each single actor, and tried to make a game that had twohundred different actors.
As far as I know he never got it anywhere near to finish, but that would have used up 4000 variables just for actor values, just because he planned it that way instead of using plugins and keeping to a reasonable number of actors...