Plenty of Facebook groups have morphed into small businesses that use outside payment and membership tools to distribute paid content (e.g. Patreon). Now, Facebook is looking at ways to bring that activity into its platform with subscription groups. These are sub-groups with exclusive content, a monthly subscription fee, and additional admin tools.
The subscription feature is currently only available to a handful of groups. Admins can charge anywhere from $4.99 to $29.99 per month for access. The content and features you get for that payment are entirely up to the admin. The $15 premium Declutter My Home group, for example, offers exclusive videos, trainings, projects, support, and more. Cooking On A Budget has weekly meal plans, tips, and shopping lists for its $10 monthly subscription.
Facebook says the idea for premium groups came from admins who wanted an easier way to manage subscriptions. However, Facebook hasn't fully committed to this feature—it's still just a test. Facebook isn't taking a cut of the subscription fees during the test, but the fees are managed as in-app subscriptions on Android and iOS. That means Google and Apple take their usual cut of sales. I wouldn't put it past Facebook to find some way to monetize subscription groups later, though.
There's no timeline on when or if subscription groups will expand to more admins. The tools and features may also change dramatically before any wider rollout. Keep an eye out in your groups for premium invitations.