Mary and Tom Poppendieck in their book Implementing Lean Software Development ask -
"How long would it take your organization to deploy a change that involves just one single line of code? Do you do this on a repeatable, reliable basis?"
You can also ask the very same question in a different way - how many engineers does it take to deploy a single line of code change? (and how much time will it take them?)
Just a sample of the questions you need to ask before coming up with an answer to that question -
How much testing will you be required to perform?
How much supporting documentation will you be required to produce?
How long will you have to wait for a test environment?
How many dependent systems will you need to test?
How long will it take to approve the change?
And, last but not least, how many of those activities add value, and how many waste time?
As Martin Fowler tweets -
An automation platform that helps you make DevOps systematic.