Aliexpress
Click here… to search for Teclast X24 Pro D3 G5400 AIO PC 8/240GB on Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (463.21 USD): BGAFF10OFF
Coupon (463.21 USD): bGhOnEy10
(CouponsFromChina.com tip: just apply this code 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): BGPC001, AFfbG10, 502C6B, BGBFAFF2019, BGCITYADS2019, bGpAnDacHeCk, 2880c7, BGMPB2020
(there’s a little possibility that old coupon will work)
Price history and price alert
Here is price history (for all/most countries) for Teclast X24 Pro D3 G5400 AIO PC 8/240GB.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).