ATM you can buy SONOFF RF BridgeR2 Smart Wi-Fi Hub 433MHz RF for $14.99 (in Banggood). Basically copy coupon, view price history or create e-mail price alert. Best price?
Working temperature: -10°C~40°C, Product Dimensions: 62x 62x 20 (mm), Material: PC V0, Certificate: CE / FCC / Declaration of EU RoHS Conformity, Power Supply: USB 5V, Security Mechanism: WPA-PSK/WPA2-PSK, Wireless Standard: WiFi 802.11b/g/n / 433.92MHz
Latest coupon and price update (UTC):
Banggood ($14.99)
Banggood warehouse is located in China. So I have checked for active coupons (all category coupons and old ones), but there was no working coupon in Banggood. Low/high price? Cool, average is $16.99, so current price is lower!
Link: Banggood product page
Price: $14.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BG364550, ADMITAD2212, BGSmart6, BG1382fb, MVC8SPRING, 8BGwbg2204, 2203ActiesNL, tRaDetRaCKeR, BGJUNEGSG9, BG15Sonoff, BG8ReviTrage, Cuponation9, 9OFFSUMMER
(there’s a little possibility that old coupon will work)
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Do you need price history chart (for all/most countries) for SONOFF RF BridgeR2 Smart Wi-Fi Hub 433MHz RF? 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)).