Read that part again. He's not claiming that $6k/month is an amazing salary (although, as I pointed out below, it is more than 70% of Americans make). When he says "a prestigious item on the resume" I'm reading that as something like taking a job at Google, which would look impressive to many potential employers.
From the perspective of a college student
I realize that HN doesn't represent the general population, but $6k/month puts you ahead of 70% of Americans. Relatively speaking, that's a very high income, not just for a college student.