Wire: RG178, Wire Length: 60mm, Wire Dia.: 1.8mm, Frequency Range: 0-6G, Impedance: 50Ω.
Just check coupons out (with price alert and history). Let’s see what best price is ATM.
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.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. So I have checked for active coupons (all category coupons and old ones), but there was no working coupon in Banggood.
Link: Banggood product page
Price: $-3
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): Parts8, BGGAL8, BGJON8, BGRCParts8
(these coupons are old, so probably won’t work)
Price history and price alert
Check out price history chart (for all/most countries) for 60mm Low Loss Antenna Extension RC Cord SMA RP-SMA. The lowest price was: $7.07.
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)).