Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (422.99 USD): Email5
Coupon (422.99 USD): bgshOOp10
(CouponsFromChina.com tip: paste coupon code in your cart and click Apply after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BG40d1c0, aff7off, BGf6df0c, bgchinafest, 7bcdf9, BG6ca9e2
(these coupons are old, so probably won’t work)
Price history and price alert
Check out price history chart (for all/most countries) for Huawei M6 CN 4/64GB WIFI Tablet Gray.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).