Aliexpress
Click here… to search for DIATONE TMC AirBlade 3inch 4K 3-4S PNP Drone on Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (215.99 USD): BGAFF10OFF
Coupon (215.99 USD): bGhOnEy10
Coupon (215.99 USD): BGdragonBoat
Coupon (215.99 USD): BGRC902
(CouponsFromChina.com tip: apply code in your basket (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): BG15TMC, AFfbG10, BGTMC9, 502C6B, BG30TMC, BGBFCR25, BGCITYADS2019, Wholesale20, 2880c7, BGMPB2020, BGSS10%SW, bgshOOp10
(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 DIATONE TMC AirBlade 3inch 4K 3-4S PNP Drone.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).