One of the remaining 3rd party Reddit apps (Relay) has begun discussing what it would be charging for subscription fees. Imo, they actually seem somewhat reasonable. The weird thing is that every upvote or downvote is an API call so you can rack up a huge number of API calls from voting.
Also, while the costs might be reasonable now, there's nothing preventing Reddit from jacking up prices again.
Edit: Also, there wouldn't be any NSFW content with the app.
As a long time relay user but not an Apollo user, my impression from reading all the drama of early June was Apollo had a lot more features than I had seen before, and that was what set it apart from other clients. More features means more API calls, generally.
As an example, I had relay poll for PM once an hour, but I remember seeing Apollo was doing it every few minutes or maybe alongside thread views so notifications were more immediate. The user experience would be better but at the expense of far more API hits.