Price history, coupons and price alert are available on this page. Let’s see what best price is ATM.
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 code price check (UTC time):
Max Current: 50A, Color: Yellow, High rate PWM: 8K, Original box: NO, Ni-Mh/Ni-cd: 4-10Ni- MH, BEC: 3A / 5V (Switch), Net Weight: 28g, Size: 45mmx 26mmx 10mm, Package weight: 37g, Li-Poly: 2-3, DC: 3.7V-14.8V, Net weight: 31g
Banggood
Banggood warehouse is located in China. I am tired of searching coupons, but I found one for you…
Link: Banggood product page
1. ($8.97): BG589b2e
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 and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): ADMITAD2212, 2022ACTIESNL, Terence, Tabby20, 8Couponsde, MVC8SPRING, 2203ActiesNL, BG00c906, BGJUNEGSG9, Cuponation9, 9OFFSUMMER
(these coupons are old, so probably won’t work)
Price history and price alert
Check out price history chart (for all/most countries) for XXD HW40A 40A Brushless Motor ESC.
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)).