Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (172.31 USD): BGAFF10OFF
Coupon (172.31 USD): bGhOnEy10
Coupon (172.31 USD): BGdragonBoat
(CouponsFromChina.com tip: just apply this code in your cart 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): 9OFFGTM3, TTxBG10, e2bcea, 502C6B, BGss9%rc, bgssaff9, AFfbG10, BGBFCR25, BGCITYADS2019, BGVDay10%off, BGMPB2020
(there’s a little possibility that old coupon will work)
Price history and price alert
Price history (for all/most countries) for Diatone 2018 GT-M3 Drone is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).