You can create price alert here, copy coupons and view price history. You probably want to know what is the best price?
Rated Voltage: 220V, Sleep Mode: 20dB, Model: MJXFJ-150-A1, Brand: Xiaomi Mijia, Applicable Area: ≤53m², Wireless Connection: IEEE802.11b/g/n 2.4GHz, Rated Frequency: 50Hz, Noise: ≤36dB, Auxiliary Heating Power: 400W, Rated Air Volume: 150m³/h, Rated Power: 20W
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):
Banggood
Banggood warehouse is located in China. Only one coupon available!
Link: Banggood product page
1. ($514.79): BG10OFFAFF1
this code has to be applied 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): 7bcdf9, BGCuponation10, BG10OFFAFF, BGwhielabel
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for Xiaomi Mijia MJXFJ-150-A1 Wall-mounted Air Purifier.
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)).