I'm sure I'm in the minority here. When I see these kinds of comments, the first thing I think of the movie Good Will Hunting:
You wasted $150,000 on an education you coulda got for $1.50 in late fees at the public library.
You wasted $150,000 on an education you coulda got for $1.50 in late fees at the public library.
The negative feedback loops are particularly hard to set up by yourself. At some point if you're going to be at the researcher level (construed broadly), you need help from others in developing sufficient dept, rigor and self-criticality. Others can poke holes in your thoughts with an ease that you probably can't muster on your own initially; after you've been through this a number of times you learn your weaknesses and can go through the process more easily. Similarly, the process of preparing for comprehensive exams in a PhD (or medical boards or whatever) is extremely helpful, but not something most people would do by themselves--the motivation to know a field very broadly and deeply, so you can explain all of this on the spot in front of 5 inquisitors, is given a big boost by the consequences of failure, which are not present in the local library.
The time is also a hard part. There are relatively few people with the resources to devote most of their time for learning outside of the classroom. I spent approximately 12,000 hours on my PhD (yes some fraction of that was looking at failblog while hungover etc. but not much). You could string that along at 10 hours a week, 50 weeks a year, which is a 'serious hobby', but it would take you 24 years. How much of the first year are you going to remember 24 years later? How will the field have changed?
Does the rest of the movie support that claim? Will Hunting had book smarts but required significant effort from several people to get him to the point where he was ready to meaningfully apply his intelligence.
I've hired a handful of folks who learned solely by self-study and while none of them required the level of support Will did, they all took significantly more effort to get to the point where they contributed productively than hires who attended university or had previously collaborated with experts.
Not saying that requires a degree, but even the most brilliant people benefit from collaborating with like minds.
Philosophy in specific is one long argument, 2500 years of new people showing up and saying, "Well that guy's wrong and I'm right." So much of what I needed to know to make sense of philosophical arguments is either hugely scattered or not written down at all. It was vastly more efficient just to hire an expert.
That's not to argue for the $150k education; I wouldn't know. But I don't think that taking life advice from fictional characters is much better.