Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. I am tired of searching coupons, but I found one for you…
Link: Banggood product page
Coupon (301.45 USD): BGheli3
(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): BGWA15, AFfbG10, 502C6B, BGV45012, BGBFAFF2019, BGCITYADS2019, BGD0315, BGD0312, BGV45003, BGZM15, BGVDay10%off, BGV45015, BGAFF10OFF, bGhOnEy10, BGAPR12, BGdragonBoat, BGSS10%SW, bgshOOp10, BGheli10, BgoFErTaSchInA10, BgcLuBofErtA10, BGCuponation10, BGDAVIS, BGHONEY2110, BGMATT7, Drones6, BANGGOODSD, 6GSGIT, CouponsDE, 00c906, BGheli010, 2022ACTIESNL, Tabby20
(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 Walkera V450D03 Generation II RC Helicopter BNF is here.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).