Hi @alxwrd-gelt, and welcome to the Auth0 Community!
For your first question, when you upgrade from the Free plan to the B2C Essentials plan, your billing is based on the total number of Monthly Active Users (MAUs). The MAUs from the Free plan are not included as a separate, free quota.
In your example, if you have 1,000 active customers in a month, you would need to subscribe to the Essentials tier that covers at least 1,000 MAUs. Using the pricing you mentioned, the monthly cost would be $70.
As for your second question, yes, a user who signs up via a social account and is subsequently rejected by your logic will still count towards your MAU limit for that month.
The reason is that a Monthly Active User is defined as any unique user who authenticates at least once during the billing cycle. In your scenario, the user successfully authenticates with their social provider (like Google), and Auth0 creates the user profile. The authentication event has already occurred before your custom logic (like a Post-Login Action) runs to deny them access to your application.
I hope this helps you! If you require more in-depth information about our billing process, don’t hesitate to reach out to the Sales team.
Sincerely,
Teodor.