The German city Munich will migrate back to Windows and leave Linux behind. Head of the Munich City Translation Department, Johannes Länting, tells: "The backward migration won't cause any problems for us, since our main translation editor, CafeTran, runs on Windows too ...". He continues: "Even better, many of our senior translators are privately working on Mac – and they can use CafeTran too." DPA 2017-02-11
Indeed it is one of the misconceptions of many OS fans that Open Source is free or less costly. Open Source is never free, as you need more efforts to train users and adapt your system (and you should put some efforts into the further development of the software – give back something, e.g. translating or spreading the word).
And it is bad luck if most ordinary users are unhappy (assuming that many communal employees are a kind of reluctant against such a change).
That's why it is important to insist on Free as in Freedom (or free speech) and not Free as in Gratis (or free beer), when talking about FLOSS.
Acquisition costs are not the only thing to take into account at any rate. There are maintainance costs, training costs, renewing licences, upgrading to new versions etc.
All costs taken into account, it is often more economical to choose FLOSS. But I guess it depends.
Other factors to take into account if we are talking about a public institution would include questions such as:
Should a public institution use solutions that promote vendor lock-ins? Closed file formats and standards? Should it strive for tech neutrality (not forcing public users to use a specific program)?
I am not a reformist myself, but here is one article that sums up such points, when it comes to government and public institutions and the choice of free software or not:
Measures Governments Can Use to Promote Free Software