Now that we have ep.io, Gondor, and all the other PaaS things that support Python, the ability to upload an application and scale it as much as we want isn't limited to App Engine anymore. Whereas back when it came out, it was the only service of its kind for Python. (Heroku might not have even been out for Ruby, though my memory's a bit fuzzy at that point.)

And pretty much all the other vendors use plain old SQL databases and don't have everything as a platform-specific API like App Engine does. So when the prices went up, my guess is that people realized, "Hey, why should I lock myself in to this one vendor that could raise the prices again, when I can go with other vendors that would be easier to migrate between [or switch to hosting myself later]?"