Aliexpress
Click here… to search for SONOFF RF BridgeR2 Smart Wi-Fi Hub 433MHz RF on Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. There are no active coupons for this product, but the price is pretty low isn’t it?
Link: Banggood product page
Price: -3 USD
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!
Old coupons (from the oldest to the newest): BG364550, ADMITAD2212, BGSmart6, BG1382fb, MVC8SPRING, 8BGwbg2204, 2203ActiesNL, tRaDetRaCKeR, BGJUNEGSG9, BG15Sonoff, BG8ReviTrage, Cuponation9, 9OFFSUMMER
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Price history (for all/most countries) for SONOFF RF BridgeR2 Smart Wi-Fi Hub 433MHz RF is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).