Cable Length (m): 1.2m, Frequency response: 20-20000Hz, Impedance: 18ohms, Sensitivity: 106db.
Just check coupons out (with price alert and history). What is the best price?
Aliexpress
I could not find it on Aliexpress. Click here to search by yourself.
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
1. ($12.31): EARSP11
2. ($12.31): BGAFF10OFF
this code has to be applied in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): TTxBG10, aff7off, BG3CSUM, bgssaff9, AFfbG10, 502C6B, BGBFAFF2019, BGCITYADS2019, BGVDay10%off
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Price history (for all/most countries) for KZ ZS3 Detachable Earphones is here. The lowest price was: $4.99.
Price records source(s): Gearbest, 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)).