Model: MR442-A, Purified Water Flow: 2.0L/min (Purified Water) / 1.05L/min (Pure Water), Rated Voltage: 220V, Rated Power: 55W, Ambient Temperature: 4℃~40℃, Rated Total Water Purification Volume: 1500L (Purified Water) / 4000L (Pure Water), Brand: XIAOMI, Water Inlet Pressure: 0.1-0.4MPa, Rated Frequency: 50Hz, Applicable Water Temperature: 5℃~38℃.
Basically copy coupon, view price history or create e-mail price alert. 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 price update (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($592.92): Terence
2. ($592.92): 2203ActiesNL
3. ($599.30): BG00c906
you should apply the coupon in your cart 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): BGHOMEA13, 7bcdf9, BGCuponation10, BG10OFFAFF, BGwhielabel, BG10OFFAFF1, 6GSGIT, 00c906, ADMITAD2212, 2022ACTIESNL, Tabby20
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Price history (for all/most countries) for Xiaomi MR442-A Water Purifier H400G is here. The lowest price was: $461.96.
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)).