If you're looking for a no-code solution to handle user authentication and monetization for your ChatGPT plugins, PluginLab is a great option. It has a fast setup option with an authentication portal that supports multiple OAuth providers and monetization through Stripe with features like real-time event tracking and tool integration with REST API and SDKs. With three pricing tiers, PluginLab is geared to accommodate a range of usage levels, so it's a good option for ChatGPT plugin authors.
If you're looking for a more general-purpose authorization service, check out PropelAuth. It's a multi-tenant authentication and authorization service with features like self-service UIs, SAML support and customizable roles and permissions. PropelAuth supports multiple sign-in options and has advanced security options, so it's good for B2B products and companies of any size. Its pricing is transparent with multiple tiers to accommodate different needs.