According to my DB the lowest price is 12.99 USD for Drill Bit Depth Stop (in Banggood). Just check coupons out (with price alert and history). Let’s see what best price is ATM.
Latest coupon and price update (UTC):
Banggood (12.99 USD)
Banggood warehouse is located in China. I’m afraid that there’s no working coupon in Banggood. Good or bad price? Hmmm, price is higher than average (which is 8.66 USD right now), so better set price alert down below…
Link: Banggood product page
Price: 12.99 USD
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Aliexpress
Click here… to search for RUITOOL Aluminum Alloy Drill Bit Depth Stop Collar Locator on Aliexpress
Here are coupons that you can use.
Price history and price alert
Here is price history (for all/most countries) for RUITOOL Aluminum Alloy Drill Bit Depth Stop Collar Locator.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).