"College" really represents two separate asset classes: education and credentials. Education leads directly to productivity. Domain-specific education (like what college provides) is not a commodity: its value is not directly market-based. An education does not become more valuable based on demand. The value depends on who has the education, their ability to apply it to the current situation, and the current state of the domain. It can also depend, to an extent, on the number of people with similar education, but this is a very slow-acting force: it can take generations to have any effect. That sort of "slowness" will tend to retard bubbling.
Credentials are a tricky subject as well. The particular credentials we're talking about have value because people trust in their correlation with education. These are much closer to a commodity, because the job market is aware of credentials. Demand for credentials can increase their value. Credentials can, therefore, bubble.
Now, if you're going to college for the education, that's fine. You'll get the same result regardless of what the market for credentials does. If you're going for credentials, you might get caught in the bubble. What's worse, if you're going for the credentials, your education will be of a lower quality than someone going for the education.
The measurable benefits of college (i.e. technical abilities) are largely obtainable without going to college. A substantial investment in effort and materials is required, and perhaps the final product does not attain that achieved by a college education. But the difference in achievable technical skill probably does not warrant the difference in price between the two options (excepting cases like certain sciences where experience with specific laboratory procedures is highly valuable).
The price of college is therefore primarily the price of a credential, and of the "intangibles." As my parent argues, credentials are bubblable; and as the OP argues, the market value of intangibles is (nearly by definition) a product of social factors, and advertising - hence subject to "bubbles" (by which I take it we mean wild price fluctuations unrelated to the underlying asset's value).
Personally, I think the price of college is really the price of a credential of the intangibles - belonging to a certain class in which there are a set of prioritized attitudes and shared cultural idioms, and a shared experience. This hypothesis suggests an incentive toward uniformity of experience among educational institutions - which (I opine) can be observed quite widely.
I disagree with your first point, but I upvoted because it is a well-stated, intelligent argument.
While it's true that you can get an education without going to college, college is a more efficient mechanism than most. They typically cover a variety of things that are not obviously important to someone studying independently (algorithmic complexity would be a good example), and (much like with a startup) the possibility of failure is an effective motivator.
It's certainly not the best solution for everyone -- not everyone learns the same way -- but there are a lot of people for whom it is a good choice.
Credentials are a tricky subject as well. The particular credentials we're talking about have value because people trust in their correlation with education. These are much closer to a commodity, because the job market is aware of credentials. Demand for credentials can increase their value. Credentials can, therefore, bubble.
Now, if you're going to college for the education, that's fine. You'll get the same result regardless of what the market for credentials does. If you're going for credentials, you might get caught in the bubble. What's worse, if you're going for the credentials, your education will be of a lower quality than someone going for the education.