You can create price alert here, copy coupons and view price history. You probably want to know what is the best price?
SONOFF M5 80 SwitchMan Smart Wall Switch APP Control Work with Alexa Google Home and Siri shortcut – 2 Gang
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):
Banggood
Banggood warehouse is located in China. CouponsFromChina software could not find any coupon for this product in Banggood.
Link: Banggood product page
Price: $-3
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BG58024b, Cuponation9, BGsonoff30, BG8ReviTrage, BGa16d12
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Do you need price history chart (for all/most countries) for SONOFF M5 80 SwitchMan Smart Wall Switch? 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)).