Aliexpress
Click here… to search for 4Pcs Xiaomi 2212 800KV 2-4S RC 1080p Motors on Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (10.99 USD): a0e5bc
Coupon (20.69 USD): AFfbG10
Coupon (21.38 USD): aff7off
(CouponsFromChina.com tip: coupon code has to be applied in shop’s cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Old coupons (from the oldest to the newest): TTxBG10, BGss9%rc, bgssaff9, rccle30off
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Price history (for all/most countries) for 4Pcs Xiaomi 2212 800KV 2-4S RC 1080p Motors is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).