In my experience, the main cost to adopting F/OSS for office software is interoperability with people sending word and excel files, not support or training.
Note, LibreOffice is available in the native language of the users, Valencian, and has spell-check dictionaries for that language. Presumably, the Valencian government puts out most communication in Valencian, so there may actually be savings in not having to develop and maintain their own Valencian dictionary for Office, which Microsoft does not provide, and reduced support as the interface uses terms more familiar to the native Valencian speakers.