I have just checked coupons. The lowest price I could get is 6.99 USD for Center Drill (in Banggood). Basically copy coupon, view price history or create e-mail price alert. Let’s see what best price is ATM.
Latest price update (UTC time):
Banggood (6.99 USD)
Banggood warehouse is located in China. I have no active coupons for you right now. Is it a low price? Hmmm, price is higher than average (which is 6.66 USD right now), so better set price alert down below…
Link: Banggood product page
Price: 6.99 USD
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BGWDT15
(these codes were not working in latest coupon update, but you can check them out anyway)
Aliexpress
Click here… to search for 6Pcs 1.0-5.0mm High-Speed Steel Center Drill Bits Set on Aliexpress
Here are coupons that you can use.
Price history and price alert
Here is price history (for all/most countries) for 6Pcs 1.0-5.0mm High-Speed Steel Center Drill Bits Set.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).