The Private cluster has no limits in terms of database size, requests, function calls and max connections etc. Instead you pay directly for the hardware required to sustain your desired load. The cluster will scale automatically to meet demand, but you can set in place limits, if you want to be in control of the monthly cost.
We are currently working on benchmarks for different scenarios to give an idea of the cost associated with running different workloads.
Hope that makes sense Regarding Brazil:
AWS ECS is currently required to deploy a Graphcool Cluster. ECS is not currently available in Brazil, but that might change soon. I suggest you check in again after AWS reInvent next month where amazon typically announces a lot of new additions like this.