The specific answer to your question is that in my experience that price includes all costs, but you won't know for sure until the phone is taken to Fedex or whoever and they fill out the customs paperwork.
My suggestions is save the money and trouble and potential hold up in customs and have a friend bring it over, or buy one in Hong Kong.
By the way, from what I read an unlocked phone you buy in the US (T Mobile version) is not going to work on China Mobile's fastest LTE network in China because it does not support the band CM uses for LTE. You should get 3G or perhaps 4G service though. I'm really not an expert, have just been doing a little reading... But if you want a phone that is likely to work on the fastest networks in China then buy the phone in China or Hong Kong.
You can look at this thread for a more detailed discussion.
https://forums.macrumors.com/threads/1773579/