Latest update shows that 1500/3000 Grit Diamond Knife Sharpener costs $5.99 (in Banggood). Go down and check coupons out. Remember to check price history if it is available. Best price?
1500/3000 Grit Diamond Knife Sharpener Sharpening Stone Whetstone Professional Woodwork Knive Grinding Edge Tool Anti-skid Base – 3000#
Latest coupon code price check (UTC time):
Banggood ($5.99)
Banggood warehouse is located in China. I’m afraid that there’s no working coupon in Banggood. But wait a sec… Is it a good price? This price is higher than average price ($4.75) for this item.
Link: Banggood product page
Price: $5.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGWDT15, BG6e5da5, BG76cfa1
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Do you need price history chart (for all/most countries) for 1500/3000 Grit Diamond Knife Sharpener? There we go.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).