$8.99 – Bike Taillight 600mAh Battery 4 Light Modes USB-C Rechargeable IPX6 Waterproof Wear-resistant Lightweight Bicycle Rear Light for Night Cycling.
Right now the best price with coupon code for Bike Taillight 600mAh 4 Light Modes USB-C Rechargeable IPX6 is $8.99 (in Banggood). Just check coupons out (with price alert and history). Best price?
Latest coupon and price update (UTC):
Banggood ($8.99)
Banggood warehouse is located in China. I don’t think there is an active coupon right now – at least in my database. Is it a reasonable price for this item? Hmmm, price is higher than average (which is $6.99 right now), so better set price alert down below…
Link: Banggood product page
Price: $8.99
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BGTYMAR43
(there’s a little possibility that old coupon will work)
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Here is price history (for all/most countries) for Bike Taillight 600mAh 4 Light Modes USB-C Rechargeable IPX6. The lowest price was: $5.99.
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)).