Amazon Cognito's default settings and MAU definition can unexpectedly increase costs

Amazon Cognito user pools are billed based on Monthly Active Users (MAUs), with costs varying across three feature tiers. New user pools default to the 'Essentials' tier, which costs nearly three times more than the cheapest 'Lite' tier. The MAU definition includes operations initiated by administrative code, such as user attribute queries, not just direct user sign-ins. These default settings and broad MAU counting often lead to unexpectedly high bills as an application's user base grows.