Pipelines causes large download costs when using ECR

We are using pipelines alpha.

Because pipelines now supports ECR it is using the AWS api to download ECR images into North Virginia from my ECR region.

This causes an inter-region data transfer which costs 14c per GB. Last month this cost over $100 USD just to run our many pipelines last month.

This would be less of an issue if the docker images were cached, which would also speed up the pipelines setup.

Alternatively, we should know which regions pipelines runs in (i suspect only North Virginia) so we can move our ECR images into so prevent this data transfer.