CEO of EMS Press here (publisher of the European Mathematical Society). Like most society publishers, we really care about our discipline(s) and want to support researchers regardless of whether they or their institution can afford an astronomical APC or subscription rates.

Good publishing costs money but there are alternatives to the established models. Since 2021 we use the Subscribe to Open (S2O) model where libraries subscribe to journals and at the beginning of each subscription year we check for each journal whether the collected revenues cover our projected costs: if they do we publish that year's content Open Access, otherwise only subscribers have access. So no fees for authors and if libraries put their money where their mouth is then also full OA and thus no barriers to reading. All journals full OA since 2024. Easy.