Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (305.90 USD): BGAProjector
Coupon (312.70 USD): BGProjectors
Coupon (330.89 USD): 7bcdf9
(CouponsFromChina.com tip: coupon code has to be applied in shop’s 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): Messenger Only, e2bcea, BGA5PRO, TECH8%, Wholesale20, BG3CSUM, bgssaff9, BGaDmITAd, BGBFAFF2019, BGCITYADS2019, aff7off, Email5, bGhOnEy10, BGdragonBoat, BGAFF7OFF, bgshOOp10, BgoFErTaSchInA10, BGAFF10OFF
(probably won’t work, but you can try them out)
Price history and price alert
Check out price history chart (for all/most countries) for Wowoto A5 Pro DLP Projector.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).