I remember being at the end of my degree and a bunch of us were sitting in the cafeteria complaining about how we hadn't learned anything. Then we realised that we were just talking about facts (and of which we had actually learned a lot - especially about underlying systems rather than factoids), but we had ignored a ton of soft skills in terms of research, collaboration, scientific procedure and rigor, self-expression, critique of other's work rigor, ethics, and plenty more I can't think of right now. In particular, it taught us how to learn further. This is a skill that a lot of people don't have. There are plenty of autodidacts, but they are definitely a small minority of people.
A smattering of online courses doesn't cover most of these items in the same manner or depth. It was certainly more than 'an old boys network', especially for me, since I have kept in contact with 0 people from those days.
Is it worth 300k? Maybe not[1]. But I didn't pay for a US university, and I've seen here on HN that there are claims that such sky-high figures are not the norm, and that there are plenty of ways to get cheaper degree-level education.
[1]Well, it was 'worth 300k' in a way - it changed who I was as a person for the better, and the way I look at new information. But I wouldn't have gone 300k into debt at the time. I did go about 40k into debt though (via HECS)