Aliexpress
Click here… to search for JmGO S3 4K Laser Projector English Version on 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 (2797.37 USD): BGAFF7OFF
Coupon (2998.92 USD): 7bcdf9
Coupon (3000.92 USD): Email5
Coupon (3000.92 USD): bGhOnEy10
(CouponsFromChina.com tip: apply it in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Old coupons (from the oldest to the newest): aff7off, BGaDmITAd, bgchinafest, BGS301, BGS34K, BGBinkupon123, BGBFAFF2019, BGCITYADS2019, bGpAnDacHeCk, BGdragonBoat, bgshOOp10, BgoFErTaSchInA10
(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 JmGO S3 4K Laser Projector English Version.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).