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 (110.02 USD): BGDAVIS
Coupon (110.59 USD): 7bcdf9
(CouponsFromChina.com tip: put item in your cart and apply coupon code there 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): BGMantis85, AFfbG10, 502C6B, BGBFCR25, BGMantis, BGCITYADS2019, BGMPB2020, BGAFF10OFF, bGhOnEy10, BGdragonBoat, BGVMantis, BGSS10%SW, BGMantisD, bgshOOp10, BGRC902, BgoFErTaSchInA10, BgcLuBofErtA10, BG11PP12, BG10RACING
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Here is price history (for all/most countries) for Happymodel Mantis85 Drone BNF.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).