Incredibly high performers exist, but are rare.

For example, the following quote is from a talk given by Gabe Newell.

(Unfortunately, I do not have the URL to the source video for this quote.)

“At IBM in the 1980s, typical productivity would be 1,000 debugged, shipped lines of code per year. That was the metric that they used for their median employee. Where as, when we were shipping Half Life 1, one employee, Yahn Bernier, was shipping 4,000 lines of code per day.”