Basically copy coupon, view price history or create e-mail price alert. Best price?
Diagonal Measurement: 84 inch, Screen Area: 186cm X 105cm, Screen Format: 16: 9, Gain: 1.1, Screen Material: PVC
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. ($650.42): BGAProjector
put item in your cart and apply coupon code there 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): 2a7e4a, od7off, Messenger Only, 1225CAR, PICODICOM, TECH8%, aff7off, bgssaff9, BGaDmITAd, 0e7f33, BGMPB2020, FBCOUPON1, bGhOnEy10, BGdragonBoat, bgshOOp10, BgoFErTaSchInA10, BgcLuBofErtA10, BGAFF10OFF, 7bcdf9, BGHONEY2110, BGProjectors, BGPROBuscape, BGLaurent, Cityads2210, Tabby20
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Do you need price history chart (for all/most countries) for 84 Inch Projector Screen 186cm x 105cm? There we go.
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)).