Basically copy coupon, view price history or create e-mail price alert. What is best price?
4x HQ Prop Duct 3″ Cinewhoop Propeller, 4x GEPRC SPEEDX GR1408 3500KV Motor, 1x Donut” 3 Inch 140mm Frame, 1x MAMBA F405 Mini MK2 25A ESC
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. I found coupon for you. Check this out.
Link: Banggood product page
1. ($140.25): BGJON8
apply it in your 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/5cd
Old coupons (from the oldest to the newest): AFfbG10, BGVDay10%off, BGAFF10OFF, BGTT10, bGhOnEy10, BGdragonBoat, BGSS10%SW, bgshOOp10, BGRC902, BgoFErTaSchInA10, BgcLuBofErtA10, BG11PP12, BGCuponation10, BGDAVIS, BGHONEY2110, Parts8
(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
Do you need price history chart (for all/most countries) for Donut 140mm F405 GR1408 Combo Drone? There we go.
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)).