The point is that it used to be $200 w/ 2-year contract, which is a huge price decrease.
Plus, it's perfectly possible to buy stuff on Amazon using a standard smart phone.
The Fire Phone does have a better camera, but aside from that I see little reason to commit to the Amazon ecology and isolate oneself from the convenience and flexibility of standard Android.
The Facebook phone went from $99 to $0 on AT&T after a month or two, and it ultimately flopped. I suspect the Amazon phone is going to flop as well.