Obviously there is a limit. Someone with 50 closest friends at high school probably won't get much work done and is unlikely to earn twice that of normal. Also someone with great grades and few friends cannot be compared with someone with many friends and bad grades.

But the doctor who had one friend at high school is probably going to be earning less than the doctor who had 5 friends. The larger number of friends demonstrates a greater comfort functioning in a group, as well as the ability to maintain several relationships at once.