Yep, open-source is 'free' as in puppy. The TCO of open source software is not zero. It's just that some people are willing to absorb those external costs.

When I, as a developer, have an issue with some open source code, I spend some amount of time fixing it (labor cost), and some amount of time with a broken system (downtime). But it's not a big deal for me, if I spend 30 minutes troubleshooting a problem. Scale that up to a company with thousands of employees, and those can be big costs.