3900mAh(min), OS MIUI 10, (1×2.84GHz + 3×2.42GHz + 4×1.80GHz), Battery(Built-in) 4000mAh(typ), RAM 6GB, AIE 4th Generation AI Engine, ROM 128GB, Display Size 6.39 Inch AMOLED, Kryo 485, MI Turbo Yes, GPU Adreno 640, Resolution 2340*1080 Pixel, 7nm, CPU Qualcomm Snapdragon 855 Octa Core (max to 2.84GHz), Game Turbo Yes. 2.0.
Basically copy coupon, view price history or create e-mail price alert. 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 price update (UTC time):
Banggood
Banggood warehouse is located in Hong Kong. There is one coupon available! Pretty cool, huh?
Link: Banggood product page
1. ($442.99): Email5
just apply this code in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BG19TP, BG29TP8, BGM9TP128, BG9TP128, BG9TP1UU, BG9TP50, BG9TPRO, BGMI9TEU3, BG9TP6, BGplmi9tp128, BG9TPCL, BG9TPCL2, BG9TP128U7, BG9TPCL3, BG9TPCL4, BGMI9TPRO128B, BG9TP6D, BG109TP, BG119TP, BG9TRGG, BG9TP6128, BG9TP855, BGD119TP855, BGHU503, BGPL119TPRO128, BG59T128, BGBFX9T128, BGBFSP9TP, BG9TPEE, BGD129TP, BG129TPBR, BG29TP, BG29TPCL
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Other warehouses/versions
This item is available in 3 another warehouse/versions!
1. Hong Kong – Xiaomi Mi9T Pro 6/128GB Global Red ($-3)
2. Hong Kong – Xiaomi Mi9T Pro 6/128GB Global Blue ($-3)
3. Hong Kong – Xiaomi Mi9T Pro 6/128GB Global White ($-3)
Price history and price alert
Price history (for all/most countries) for Xiaomi Mi9T Pro 6/128GB Global Black is here. The lowest price was: $329.99.
Price records source(s): Banggood
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)).