Making a DCF analysis for education is going to be extremely murky.

That said, since it was done in spreadsheet, it would be easy for a relatively non-technical person to tweak the numbers to refute the author's argument (sidenote: only in the world of hacker news would people think python is more accessible).

I think the lack of interest in reviewing the spreadsheet reflects how people with education department degrees protect their jobs and win public policy arguments: they prefer to argue that ROI is not a relevant concept for education investment (even if it is at the core of virtually every other type of investment analysis).