But you've made an assumption that they will be more productive in MS Office, with nothing to back that up. I've see users (particularly non-technical, "basic"

But you've made an assumption that they will be more productive in MS Office, with nothing to back that up. I've see users (particularly non-technical, "basic" users) be more productive in LibreOffice. So they may have messed the numbers up and be saving even more than they thought.