How much is the typical dutch university paying MS/Google? Maybe 10k students x 200EUR/year = 2 million EUR/year.

Twenty universities come together to move to make Collabora+NextCloud work for them. That's 40 million EUR/year. How much do they need to actually spend on developers + infrastructure to make it happen?

They probably paying a tenth of that as big edu users. What you quote are the commercial starting price for a basic-ish license.

If you look at the numbers that way, open source usually looks like a slam dunk.

The problem is coordination issues: actually getting people and orgs to look at it that way and spend the money that way, rather than just waiting for someone else to fix the problem.