After many times I have seen the parent company DT not selling well some of their devices I think TMUS can sell them in the USA to help gain more variety and increases sales where their loses. I have seen some smartpones sold by the parent company that my help TMUS product line. Just a though.
Device contracts between countries can vary pretty greatly, so that is largely a reason for the difference. That said, definitely something we are always wanting to work on, so we appreciate the feedback!