$9.99 – Function: Light Sensor+Motion Sensor, Light Color: White Light, Working Temperature: -5℃~+38℃, Size: 81*46*30mm, Shell Color: White/ Silver (Optional), Power Supply: 1pc 1.5V AA Battery (Not Included), Sensing Range: 3m 120°, Light Source: 4pcs LED.
I have just checked coupons. The lowest price I could get is $9.99 for Home Infrared PIR Keyhole Light (in Banggood). Get coupons, create price alert or check price history out! Best price?
Latest coupon code price check (UTC time):
Banggood ($9.99)
Banggood warehouse is located in China. I’m afraid that there’s no working coupon in Banggood. Low/high price? Maybe there’re no more promotions for this item, because current price is higher than average (which is equal $6.21)
Link: Banggood product page
Price: $9.99
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BG589b2e
(I don’t think these’re gonna work, but you can try ’em out anyway)
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 Home Infrared PIR Keyhole Light. 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)).