CMCC version (chinese logo on the box. The rest is the same), CPU: Snapdragon 625 2.0GHz Octa Core, Display: 5.5 inch, 1920x 1080 Pixel LTPS FHD screen, 450nit brightness, 403ppi, 4GB RAM, 64GB ROM, System: MIUI 8, Camera: 5.0MP front camera + 12.0MP + 12.0MP back cameras.
You can create price alert here, copy coupons and view price history. Let’s see what best price is ATM.
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest coupon and price update (UTC):
Price history and price alert
Check out price history chart (for all/most countries) for Xiaomi Mi5X 4/64GB CMCC Black. The lowest price was: $185.99.
Price records source(s): Gearbest
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).