You can create price alert here, copy coupons and view price history. You probably want to know what is the 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 price update (UTC time):
Humidity Accuracy ±1% RH, Wi-Fi Support 2.4G IEEE 802.11 b/g/n, Temperature Measure Range 0℃-60℃, Power Supply DC 5V/1A, Measure Range 0% RH~99% RH, Size 65*65*17mm/2.5*2.5*0.6in, Temperature Accuracy ±1 Humidity, Weight 45.8g, Material ABS
Banggood
Banggood warehouse is located in China. I found coupon for you. Check this out.
Link: Banggood product page
1. ($20.67): BG589b2e
just apply this code 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): BG21DC4, BGwhielabel, BGTUYA174, BGJUFR374, BGYR374, BGJUFO374, BGPDhome45, BG10OFFAFF1, BGTYOC374, BGISOG374, BGSPHOME35, BGTYSR374, BGTYSK374, BANGGOODSD, BGTYOU374, BGUdb49, BGUbf44, BGTYOP374, BGTYOI374, 00c906, BGJATY374, BG00c906, BGHealth10D, 2022ACTIESNL, BGHB218, BGGRMA156, BGMAYB234, BGXPAP67, BGGRAP141, 2203ActiesNL, BGHECARE1, BG2294d8, BG1c4b4a, BGHUXC038, BG77a473, BG4ee866, Cuponation9, BGb8a272, BG75597c, BG21b480, BGe7add4, BGfe422c
(probably won’t work, but you can try them out)
Price history and price alert
Check out price history chart (for all/most countries) for Tuya WIFI Temperature Humidity Smart Sensor.
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)).