Interesting that you paid attention to his salary. What about his course work? What about the hardware and languages he knows? He was more skilled than the average developer today in his freshman year.
Oh,I've seen that part as well, however there were also some very good comments made by other users on that section.Bill was doing stuff on a computer since the childhood,so by the time he walked into the uni he already knew more than an average guy.
His developer chops were why he was making such bank at 18 years old. Still though, his salary is probably the most interesting takeaway from all of this (that, or the whole listing your height & weight thing).