There has been a lot of confusion and complaining about the price increases, and this is understandable given the way it has come about. This is one of those oh so obvious things, but you just have to look at it and evaluate. Besides scalability, app engine can be a great platform from a rapid app development standpoint. It has other nice aspects in addition to the scalability.

And don't forget to look into what may be able to be done to minimize some of the quota impact. Good design changes may be able to have a noticeable positive effect there.

Have a look at AppScale if you are looking at moving off the platform. That may be a way to get 80% of the way there with less monumental changes.