Brand: Aqarax EigenStone, 50/60Hz, Model: KTWKQ03ES, Wireless Protocol: Zigbee, Operatring Temperature: -10℃-50℃, Temperature Display: 0-40℃, Operating Voltage: 85-250VAC.
Basically copy coupon, view price history or create e-mail price alert. What is best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($56.30): MVC8SPRING
2. ($56.30): 8BGwbg2204
put item in your cart and apply coupon code there after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): bgshOOp10, BGSAMRTH, BgcLuBofErtA10, BG15SH12, BGSTHO15, BGHONEY2110, BGSHOM15, BGSHE15, 13f142, BG57f09c, BGAQA929, BG4a7a54, ADMITAD2212, BGSmart6
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Price history (for all/most countries) for Xiaomi Aqara EigenStone S2 ZigBee Smart Thermostat is here. The lowest price was: $39.99.
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)).