Let's do some back-of-the-napkin math. Selig estimates that the average user would cost him $2.50/mo and his annual costs would be $20m/yr, so it seems like Apollo has 600–700k monthly active users — something like 0.16% of all 430m active Reddit users. That is simply not going to represent a significant opportunity cost to Reddit's overall ad revenue.

Plus, I'd bet that third-party app users are far more likely to be mods and/or heavy content creators, which means that alienating them will have outsized negative effects on the engagement of the rest of the userbase.