I frequently hear the question at conferences... sure, we all know we should write tests, but it's like exercise. I know I should, but I don't. It would take too much time.
Recently I've been telling people that it takes only 10% of their time to create automated tests. And then I tell them about this blog entry. I decided to link to it so it'd be easier to find.
Automated Testing -- It's the thought that counts
At 6th Sense Analytics, we collect process metrics, so this is just an example of the type of insight we can pull out. After the tests were created, we knew exactly how much time was required.