Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. There is no active coupon in my database right now (for Banggood).
Link: Banggood product page
Price: -3 USD
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!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BGa380c5, MVC8SPRING, BGJUNEGSG9, Cuponation9, COUPONSDE1wk, BgGoodie9, BGcoupon8off, BGGutscheine, BGTOOS729
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Price history (for all/most countries) for HackRF One 1MHz to 6GHz USB Radio Platform SDR RTL is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).