With App Engine you pay only for your resource consumption. The resources are provisioned with granular units called "Cloudlets". This allows to allocate exactly the needed amount of resources.
1 Cloudlet = 128MiB of RAM and 400MHz of CPU
You have a choice between a dynamic, cost-efficient model (usage-based) and a traditional model with fix pricing (reserved).
With this model, the price is variable as you pay only for what you really use. For instance, during the day there is high load of your application (you pay more) and at night there is low load (you pay less).
The discount level is the total sum of all dynamic cloudlets in use per environment.
With this model, you pay a fixed price. You always pay for the configured (reserved) number of Cloudlets, even if you use fewer resources.
The discount level is the total sum of all reserved cloudlets per environment.
Disk space is charged hourly per GB of disk space used in your environment.
This is about an external, public IPv4 address which is directly accessible from outside of the cluster. Charges accrue hourly for as long as the public IP exists.
1 TB External Traffic. Per environment 1 TB of external traffic per month is included. Traffic above the included quota, costs CHF 0.06 per GB per month. Internal traffic is always free.
You probably ask yourself: how much does it cost me exactly per month? Well, this is always different as it depends on your application load. Therefore, we recommend anybody: