[hinkley]

You're going to run a production system with a bus number of 1?

I think you mean a small fraction of 3 engineers. And small fractions aren't that small.

[adrianN]

So far I have seen a lot more production systems with a bus factor of zero than production systems with a bus factor greater one.

[xboxnolifes]

The cost being a fraction of 1 does not imply it's one person. 3 people each spending 2 weeks a year on the service is still a fraction of 1.

[hinkley]

It is three opportunity costs. No free lunches.

[Dylan16807]

Nobody implied it was free. Yes there are opportunity costs, and they add up to less than one sysadmin of opportunity.