> The debate you seem to be aiming toward is whether we should have public universities

Apologies if my argument came out that way. I agree with a need for public universities, I just disagree with the need to have them at any cost. Ad absurdium, a public university that costs $1,000 / $10,000 / $100,000 / $1,000,000 per student are all a good deal to a purist because hey, a need is a need.

The current system, however, incentivizes extracting maximum value for the stakeholders (administration) while delivering minimum results to customers (students). With a single-payer there's even a stronger incentive to inflate the operating costs.

If you went through US higher education, you've probably witnessed a few tricks designed for maximum revenue extraction.

* credits from one [cheaper] accredited institution are not transferable to another [expensive one], ensuring that you'd be subjected to a higher tuition

* courses that can be delivered online are not

* courses that are delivered online are paywalled to ensure only those who have registered and paid can view the precious content (something Open Courseware stood up against)

* there's no system where one can test out of pre-requisites by taking similar courses cheaper (or free) elsewhere. E.g., if you self-studied through some MIT or Stanford courses online, you still have to pay full tuition at Fill In The Blank State University

Granted, it's not always about effort duplication and resource waste. California Community Colleges, for instance, is good at centralizing student registration, identity management, and financials, so that each community college doesn't have to run a fully staffed department doing all that.

Ideally, though, an eager high school student should be able to

* load up on as many courses as they can manage online on their own schedule

* have an ability to test out of the courses for a fee that's lower than the full price of the course

* arrive at the university and pay full tuition for the courses that do require in-person training (nursing, medical sciences, any course requiring labs)

You're right, end of the day a public university is an extension of secondary school, but with higher concentrations of students (and hence fewer locations required and all sorts of economies of scale at play). There's no reason that grades 13-16 should cost more than grades K-12, so why do they?

> disagree with the need to have them at any cost.

I think we can all agree with that. I think a sane position is to return to the level of state support of e.g. the 1960s or 1970s. This worked in a substantially poorer US until we chose to stop doing it.

> There's no reason that grades 13-16 should cost more than grades K-12, so why do they?

This is the key point. Like most things, this is driven by policy choices. The choice is made to achieve certain aims, or to ensure other aims are not achieved. We have the object lesson that subsidized college broadly worked in the US until we collectively decided to stop doing it. We can choose differently when there is political will to do so.

FWIW I would suspect that most of the explicit revenue extraction is less about the types of things you indicated and more about the # of full-fare international students a college is able to recruit. There's a huge difference between a $35k in-state student on financial aid and a $55k student who will pay cash.