Okay, maybe not impossibly high, but definitely out of the reach of mortals.
This query on the data explorer shows that the top few users have effectively been earning several hundred rep points per day, every day, since the site launched.
Under the current rules, with the rep cap of 200, that should be virtually impossible. You could do it if you got a bounty or two every day as well, but it's still a tall order.
Is that really realistic? Or have the rules changed over time?