Total cost of ownership is 4 years x $15k-$25k (for a cheap public school) + missed income from working that same four years ($35k x 4 years). This is equal to $220k +/- $20k of lost money.

Now compare this to income differential. Starting grad income is $80k(?). At 4% raise per year compared to 3.5% raise per year for a non-college employee. Over 43 years.

My math comes out to the college grad is still making more money despite the initial sunk cost.

Anecdotally my wife came very close to finishing a 4 year degree but ultimately did not for various reasons (she comes from a very disadvantaged family...) and not having one has been a major burden or blocker for her pursuing all kinds of jobs. I am hoping to help her finish, but it is hard to restart later in life and lots of past credits will probably be lost or not count anymore due to various academic bureaucracy roadblocks.

This assumes that every college grad is guaranteed a decent starting income. It seems that on average new grads are struggling more now than they used to to get jobs in their fields, especially higher paying jobs. And that perception is probably magnified by internet horror stories such as every 3rd post on r/cscareers.

Assuming a grad income of $80k is an insane starting assumption. MAYBE you’re making that in software (good luck getting your foot in the door).

Any other industry? Biology? Social sciences? Academia? Manufacturing?

I struggle to think of anything other than finance that has a shot of STARTING at $80k. Hell I didn’t hit $80k in software industry until ~3 years in and I thought I was (I indeed WAS) very lucky.

I'm not sure where your numbers come from. In my region job prospects are not much better for a liberal arts grad than a high school graduate, and much, much worse than someone with a trades education.