$9.99 – that is current price with coupon for SONOFF MINI R4 Wifi Switch Module (in Banggood). Go down and check coupons out. Remember to check price history if it is available. Let’s see what best price is ATM.
SONOFF MINI R4 Wifi Switch Module Smart Wi-Fi Two Way Switch Smart Home Works R5 S-MATE Wireless Control Alexa Google Home
Latest coupon code price check (UTC time):
Banggood ($9.99)
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. Is it expensive? Pretty good price – average ($10.27) is higher than current one!
Link: Banggood product page
Price: $9.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
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 MINI R4 Wifi Switch Module? 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)).