This sounds like good advice, and that level of communication can certainly be missing sometimes. Quite a few software projects though are one off custom jobs

This sounds like good advice, and that level of communication can certainly be missing sometimes. Quite a few software projects though are one off custom jobs where the requirements have never been implemented before (sometimes anywhere) and it does make estimating based on past performance pretty difficult. It's also notoriously hard to predict all the problems you might come across ahead of time, especially if you aren't familiar with the specifics of the code you will need to integrate with (maybe you could consider that like quoting to refurbish an old house before you've looked inside it and seen the damp patch and the hole in the roof) It does get easier with experience though, and much more so if you are regularly doing the same kind of software projects.