Not sure yet. Even though we are one of the bigger clients on App Engine we weren't getting charged much at all for our usage anyways. But I believe Google said it would be around 3x for the HRD which isn't bad at all. Our executives really didn't care though as stability and reliability to our customers is worth too much to worry 3X (GAE's non-hrd stability has not been good recently). Btw we all use EC2 for some of our other services and that is costing us quite a bit more than GAE is at the moment. We'll see if that continues to hold true as we grow.