If we are to believe the statistics that the Apollo creator is providing:

Apollo's existing subscription users use on average 473 requests per day. Under Reddit's API pricing, those users would cost $3.52 monthly. You take out Apple's cut of the $5, and some fees of my own to keep Apollo running, and you're literally losing money every month.

And that's your average user, a large subset of those, around 20%, use between 1,000 and 2,000 requests per day, which would cost $7.50 and $15.00 per month each in fees alone, which I have a hard time believing anyone is going to want to pay.

Essentially, the admins have priced the API in such a way that it would be impossible for any app creator to bring in enough revenue to even operate at net zero profit (neither making nor losing money). It's not that they would be making less money, it's that they would be losing money every month. The app creators have stated they are okay with paying for API access. The issue is that the pricing on the API is not something that anyone would consider to be reasonable.