It's actually hard to believe people are throwing this big a fit over something they don't deem worthy of $5 a month.
Had it been something like "starting next year only Premium users will get to auth to the API" (which is analogous to the $5/mo. of Discord Nitro) the lead time would have been greater and the users would have been able to solve the problem of access on their own.
I imagine this being less desirable when individuals have multiple accounts.
If you have 10,000 users that Reddit in 30 days is going to charge you $250,000 per month to continue allowing your third party app to operate and you only had 5-10% of your users paying for a premium version you could see how that becomes somewhat unreasonable.
A bit more of a heads up is all the Apollo developer wanted. He understood that the API no longer being free is reasonable. The timing is what he objects. No assistance in allowing premium Reddit accounts that use Third Party Apps to cover API costs, etc.
Plus $2.5 to Reddit, means that apps need to charge $3.60 before 30% App-Store fees. But the app developer also needs new infrastructure to handle the billing, payment, and tracking, between end-users & Reddit along with their existing overhead. So the current $1/month aka $0.70/month after fees they're operating on likely isn't sustainable.
So now we're looking at $3.60 to Reddit + the existing $1/month = $4.6, but also all this new payment/billing infrastructure. Could easily exceed $5/month which frankly nobody is going to pay, and then get all this done in just 30-days even though that date is completely arbitrary from Reddit's end.