Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in Hong Kong.
Link: Banggood product page
Coupon (2839.99 USD): BG4c253a
Coupon (2899.99 USD): BG80fa20
Coupon (2929.99 USD): BGe390b1
Coupon (3289.99 USD): BG589b2e
(CouponsFromChina.com tip: 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
Old coupons (from the oldest to the newest): BGProj, BGKTPA, BGSaleFeb8, BGSaleAD
(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 Formovie THEATER 4K Laser Projector Global UST UHD ALPD 4.0 is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).