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.
I do remember people saying that Apollo was badly optimized for API calls.
I always felt like there has been some backroom negotiations between Relay and Reddit because Relay has (allegedly) been eating the costs of the API calls. Doesn't seem like it would be cheap for the dev to just eat that cost.