As he mentions in the post, the main issue is the 30-day timeframe to completely rethink the business model of the app and move enough users over to paying subscriptions to not go bankrupt when the first API access bill comes in. The suggested API fees also seem quite unrealistic and it's unclear whether enough users would be willing to pay the necessary monthly fees to cover them.

Reddit's actions here make it pretty clear that they just want the app (all third-party apps) to shut down — if they actually wanted a solution they could easily lower the pricing to something more realistic and/or give a slightly longer transition period.