The only thing that makes sense to me is some political long play. The Amazon retail operation employs a lot more people in a lot more places than just the coast. I think leadership has realized they need to be seen as a job creator by politicians in order to join the "big boy industry" club. Which is why Amazon doesn't mind paying their warehouse workers more than all the other guys.
To that end, the Amazon.com is just a giant, self-funded employment program designed to make Amazon a bigger company.