Relay is an amazing app. Very smooth. And this is a good solution for his app to survive.
But besides the fact that almost all of the money will be going to Reddit. Everything you do on the app makes calls to the API, including voting. And each vote is equal to one call, just as much getting a batch of comments for a post, or getting a batch of posts.
So the best way to keep your API calls low is to not vote on any post or comment.
Maybe the dev will optimize this somehow by maybe batching votes and sending them at a later date, but you can see how the current situation, made possible by reddit, will decrease engagement.