Why are software development estimates regularly off by a factor of 2-3 times?

This is really a very good and readily accessible explanation why estimating a project you do not routinely execute is so tremendously hard.

This may be a story structure worth memorising. to explain why what might look like a 10 day project at face value can turn out to be a 60 day marathon.

Two posts that may be worth looking at on the theme of resourcing: