OS Joy UI (Android 9.0), Resolution 2340*1080 Pixel, ROM 256GB UFS 2.1, GPU Adreno 640, Battery(Built-in) 4000mAh(typ), Display Size 6.39 Inch AMOLED 19.5: 9, CPU Qualcomm Snapdragon 855 Octa Core, max to 2.84GHz, 3900mAh(min), RAM 8GB LPDDR4x.
You can create price alert here, copy coupons and view price history. What is best price?
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 code price check (UTC time):
Banggood
Banggood warehouse is located in China. There is one coupon right now! Check this out.
Link: Banggood product page
1. ($602.99): BGBFAFF2019
coupon code has to be applied in shop’s cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/i1u
Old coupons (from the oldest to the newest): BGBS285, aff7off, bgssaff9, BGaDmITAd
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
Price history and price alert
Price history (for all/most countries) for Xiaomi Black Shark 2 8/256GB Black is here. The lowest price was: $469.99.
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)).