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.
"Those people" were Spez and admins, who have a vested interest in actively attacking Apollo, and then ran an entire smear campaign trying to accuse Christian of blackmailing reddit when just calling his app bad wasn't enough. Nobody else ever corroborated those baseless claims made using unlabeled bar graphs. That info has exactly zero credibility, please do not repeat it.
The reality is, users that care enough about their experience to use a 3rd party app simply use reddit more. And make more api calls for content.