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 (44.68 USD): BGGines
Coupon (46.67 USD): BG00c906
(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): 7ad9a1, TOOLS15, BG2020NS, BGVDay10%off, BGAFF10OFF, BGTT10, bGhOnEy10, BGherra, BgcLuBofErtA10
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Here is price history (for all/most countries) for Professional Knife Sharpener System with 4 Stones.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).