According to my DB the lowest price is $8.99 for Eachine StingPad 5.8G 16dBi Flat Panel FPV Antenna (in Banggood). Go down and check coupons out. Remember to check price history if it is available. What is best price?
Latest coupon code price check (UTC time):
Item Name: StingPad Antenna, Connector: SMA, Gain: 16dBi, Impedance: 50 ohms, Radiation: directional, VSWR: < 1.3: 1 (5722 - 5945MHz), Beam width 42 degrees (H + V), Brand Name: Eachine
Banggood ($8.99)
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. Is it a reasonable price for this item? It’s a good price, isn’t it? The average is $10.06.
Link: Banggood product page
Price: $8.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
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:
Old coupons (from the oldest to the newest): BGEachine10, BGRCEachine, Tabby20, BGRCT10, BGToys8, BGMatt2022, BG25d4e7, BG589b2e
(you can check these old coupons out, but these probably won’t work)
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Check out price history chart (for all/most countries) for Eachine StingPad 5.8G 16dBi Flat Panel FPV Antenna.
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)).