Post also doesn’t mention this from the pricing that means existing customers in free tier aren’t being suddenly charged:

Note:

1. Customers with existing user pools created on or before 10:00am Pacific Time, November 22, 2024 will continue having a free tier of first 50,000 MAUs. Advanced Security Features (ASF) will continue to be priced separately and will not have a free tier, just like it has been priced previously.

2. Additionally, customers are eligible to create new user pools with Lite tier in their existing accounts and count those MAUs against the free tier of first 50,000 MAUs. To be eligible, customers' accounts must have had at least 1 MAU in the last 12 months on or before 10:00am Pacific Time, November 22, 2024.