The price was extremely high in comparison to what it offered: Sure, Apple charges to develop for iOS, but iOS has a few hundred million credit-card enabled customers buying software. App.net had a bunch of already-paid developers using the service.
I tried to figure out the point through a few emails with the creator but ultimately it felt like a service for developers flush with spending money to join a sort of app vanity press.
I'm glad that it's opening up now and I'm suddenly starting to get interested in the project!