Aliexpress
Click here… to search for EMAX RS2306 RACE SPEC Motor 2400KV Black on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. One coupon is available. Cool!
Link: Banggood product page
Coupon (23.91 USD): Parts8
(CouponsFromChina.com tip: this code has to be applied in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Old coupons (from the oldest to the newest): AFfbG10, 0e7f33, FBCOUPON1, BGAFF10OFF, BGCuponation10, BGDAVIS, BGHONEY2110
(there’s a little possibility that old coupon will work)
Price history and price alert
Price history (for all/most countries) for EMAX RS2306 RACE SPEC Motor 2400KV Black is here.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).