According to my DB the lowest price is $26.99 for Tuya WiFi ZigBee Smart Thermostat (in Banggood). Go down and check coupons out. Remember to check price history if it is available. What is the best price?
Tuya WiFi ZigBe Smart Thermostat Low Power Battery Water Gas Boiler Temperature Controller Work with Alexa Google Home – ZigBee
Latest coupon code price check (UTC time):
Banggood ($26.99)
Banggood warehouse is located in China. There is no active coupon in my database right now (for Banggood). Is it expensive? Well, this price is higher than average price ($25.99)
Link: Banggood product page
Price: $26.99
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 Tuya WiFi ZigBee Smart Thermostat? 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)).