Xiaomi Mi Temperature and Humidity Sensor (Banggood, Aliexpress: This item must match the Xiaomi multifunctional gateway to use, real-time detect the temperature and humidity condition, app control, Temperature measuring accuracy is -0.3 – 0.3 degree, Humidity measuring accuracy is -3 – 3 percent, Powered by 1x 3V CR1632 button battery (included) (the best price with coupon)).
Go down and check coupons out. Remember to check price history if it is available. Best price?
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 and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($12.59): BGAFF10OFF
2. ($12.99): 13f142
you should apply the coupon in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): 20XMAQ, 939404, affiliate6, aff7off, bgssaff9, BGaDmITAd, BGXMTH09, BGBFAFF2019, BGCITYADS2019, BGSORRA, 2020CNY, BGVDay10%off, BGAQ20, BGHOMEAPP, BGSMARTHO, BGXMTEM, bGhOnEy10, BGSM15, BGSMOFF, BgcLuBofErtA10
(there’s a little possibility that old coupon will work)
Other warehouses/versions
This item is available in 1 another warehouse/version!
1. Europe – Xiaomi Mi Temperature and Humidity Sensor [EU] ($-3)
Price history and price alert
Price history (for all/most countries) for Xiaomi Mi Temperature and Humidity Sensor is here. The lowest price was: $5.39.
Price records source(s): Gearbest, 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)).