Reddit’s API is not a “public pathway.” It is a private gateway into the reddit environment. They can charge whatever they like for it, because it is a part of their application.

Not saying that you are wrong, legally, and not to relitigate the whole thing again, but if you offer a public facing API and then you later on just withdraw it (or its functionality) altogether, that's something a business should not do to its customer base ever, for ethical and social contract reasons.

The Internet is not just defined by legal systems, it started with ethical social contract systems. More nebulous than legal, yes, but still, Society does follow them and expects companies to do so as well.