What you're saying is in essence correct, but I don't think that their fire phone "3d gimic" (which added very much to unit cost) was necessary to achieve that outcome.

I think it was detrimental.

A phone with comparable specs to the Moto G could have achieved their real goal that you mentioned, with the effect of spreading sales opportunities to millions more people. Those millions more in phone sales would have caused many, many more added transactions to the Amazon machine, as I assume they intend with the Amazon Fire Phone.