Quote: " does Anime Studio have an easily readable export format for game development?"
Yes, a series of .png files which they can be combined into a single texture ready to use from AppGameKit animation commands
Quote: "The basic version of Spine is currently about $60"
To be honest I don't remember the price (I store only the S/N) but I am sure it was under 100 €
Quote: "What can it do that Spine can't?"
The 'more' list is endless. Among others:
Complete set of drawing tools to draw your artwork without needing another application
Physics
Smart bones they provide precision of animation (at vertex level) around character joints
Scripting
Charcter wizard
etc
I think the comparison is unfair because the Anime Studio Pro is a complete animation package