My understanding was that if the developer didn’t make money themselves, Reddit would allow a limited amount of API use for free. What might be happening here is that the developer doesn’t get paid until they introduce subscription costs, but also has free or reduced API prices in the meantime.

To me, Reddit’s policy seems to be driven as much by spite as anything else. When it comes down to it, they don’t mind subsidizing some apps, as long as those apps don’t make money: “if we can’t make money off your app, then you can’t either” rather than “we can’t afford our server bill, pay for what you’re using.”