> You're getting lots of replies from (I presume) Americans, who are used to much scammier business behavior than what I know from Germany and you describe in Australia.

Berlin‘s public transport company has the exact condition in their terms of service.

> https://www.tagesspiegel.de/berlin/streit-ueber-monatskarten...

(„ Zudem sei eine Kündigung für Abonnenten unattraktiv, da sich für die schon genutzten Monate nachträglich der Preis erhöhe, hieß es.“)

It‘s definitely not a scam or rip-off, just a case of someone not reading the contract before signing it.