You can create price alert here, copy coupons and view price history. What is best price?
Particulate Matter CARD: 500m³/h, Replacing Cycle: 3-6 Months
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.
Link: Banggood product page
1. ($71.28): ADMITAD2212
2. ($72.05): BG00c906
you should apply the coupon in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGBWFLCN, BGHOMEA13, 10%ForNewBW, BGAP1AP2CN, 10%ForBGBW, BG10OFFAFF, BGACZBWP2, BGwhielabel, BGHU0604, BGa1da8d, BGDC727, BGa066f4, BGHU0887, BG10OFFAFF1, BG7c4b2b, BGHU0972, BGDC0932, BG0c21c6, BANGGOODSD, 6GSGIT, BGbbec2b, BGHU1166, BGDC1136, BGDBD60, BGBFD41, BGHW132, BGe2b68d, BGHUA01, 00c906, BGa52fcf, BGPL1PC, BGHUA18, BGd3dca7, 2022ACTIESNL, BGf2a6fd, BGHU0225B, BGa955a9, Terence, Tabby20, 2203ActiesNL, BGCCHU13, BG1efeb0, BGHU0418AA, BGJUNEGSG9, Cuponation9, BGAHPU13, BGbwbwbw01, BGBwwwwww01, BGLWRZESNIA6, BG8ReviTrage
(I don’t think these’re gonna work, but you can try ’em out anyway)
Other warehouses/versions
This item is available in 3 another warehouse/versions!
1. China – BlitzWolf Air Purifier Filter BW-AP1 ($-3)
2. Europe – BlitzWolf Air Purifier Filter BW-AP2 [EU] ($-3)
3. Europe – BlitzWolf Air Purifier Filter BW-AP1 [EU] ($-3)
Price history and price alert
Here is price history (for all/most countries) for BlitzWolf Air Purifier Filter BW-AP2.
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)).