>I've spent the last 4 years working on my PhD and I have learned a lot, I've made real improvements to human knowledge, and I've gotten a job that would have been impossible with a bachelors and 4 years of work experience.

The real problem with oversupply of PhDs is there are fields of study which aren't remunerative outside academia. If you get a PhD in electrical engineering, say, or something medical, you can get a job.

But if you field of study was sociology or literature and you can't find a job in academia (and you probably can't), you're never going to be able to pay of eight or ten year's worth of student loans.