Short term costs work the other way though: every company or organization needs to be able to read an office file in the latest format, edit it, and return it to the sender with full fidelity. If OpenOffice inserts a page break where MS office wouldn't have, that is a problem. The open programs read docx reasonably well, but implementing ms word clean room with all it's behaviors is near impossible, and every difference hides a cost for the users that communicate.
Within an organization you could agree to use some open format (regardless of word processor), and you could archive in some long term format. But you can't change the fact that incoming documents will be in the format that Microsofts latest word processor spits out, and you never want to have that nagging feeling that your word processor may have misread it ever so slightly.