We just announced that developers can now grow their applications beyond App Engine's free limits that have been in place since it launched last year.

The pricing for resources beyond those free quotas is:
  • $0.10 per CPU core hour.
  • $0.10 per GB of incoming traffic and $0.12 per GB of outgoing traffic
  • $0.15 per GB of data stored by the application per month.
  • $0.0001 per email recipient for emails sent by the application
For more detail, check out the post in the App Engine Blog.