According to my DB the lowest price is 9.99 USD for Astrolux TL01 Bike Taillight 500mAh (in Banggood). Just check coupons out (with price alert and history). What is the best price?
Latest coupon and price update (UTC):
Banggood (9.99 USD)
Banggood warehouse is located in China. Low/high price? This price is higher than average price (7.99 USD) for this item. I found coupon for you. Check this out.
Link: Banggood product page
Price without coupon: 12.99 USD
Coupon (9.99 USD): BGTYASR7
(CouponsFromChina.com tip: apply it in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
There were country-specific coupon codes published on Couponsfromchina social channels and price alerts. Coupon price may vary by country, because there’re different VAT rates, shipping cost etc. There is a chance that some latest coupons are still working:
Coupon (5.2.2024, $9.99): BGHUTL01
Item: Astrolux TL01 Bike Taillight 500mAh
Countries: Croatia, CzechRepublic, Hungary, Slovakia(SlovakRepublic), Slovenia
Old coupons (from the oldest to the newest): BGALTL01, BGTYTL01, BGTYTHUR1, BGTYHOT4
(these codes were not working in latest coupon update, but you can check them out anyway)
Aliexpress
Click here… to search for Astrolux TL01 Bike Taillight 500mAh on Aliexpress
Here are coupons that you can use.
Price history and price alert
Price history (for all/most countries) for Astrolux TL01 Bike Taillight 500mAh is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).