Aliexpress
Click here… to search for M3-M10 Metric Tap Drill Bits M3-M10 on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (11.67 USD): BGDRB18
Coupon (12.10 USD): BGherra
(CouponsFromChina.com tip: you should apply the coupon 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): bgsport, TA12, TTxBG10, BG18DB, TS15prime, BGAT18, bGhOnEy10, BGBFCR32
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Here is price history (for all/most countries) for M3-M10 Metric Tap Drill Bits M3-M10.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).