> OpenBSD's man pages are one example.

OpenBDS's developer to user ratio must be less that 1 to 1000s. When you update one line of document, you're probably saving time for thousands of users accross years of use.

Most project I worked on had at most a few dozen people with an actual chance of reading the documentation, and the majority of them aren't users, they'll be reading all the code anyway because they're not in a position to blindly trust the documentaton.

Why should we calculate the ROI of the time spend on maintaining good documentation the same way in both cases ?

PS: I also think a distinction should be made between specification and documentation. It feels that both are conflated too many times.