Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (804.09 USD): BGPROBuscape
Coupon (851.39 USD): BGAProjector
(CouponsFromChina.com tip: apply code in your basket (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): 7bcdf9, BGJGN7, BGAFF7OFF, BGProjectors
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Price history (for all/most countries) for JMGO N7 1080P DLP Projector is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).