I have a long-standing client who has a complex piece of software that I developed for them some time ago. From time to time they approach me and ask me to make improvements to the software, which I am almost always happy to perform. And like any good client they want an understanding of the cost before they move forward, largely to ensure that the cost-benefit analysis makes sense. And so, they ask for an estimate.
I’ve written on estimates in the past. I don’t like them, largely because they can tend to box you into a particular position that may or may not be correct.