You can get 300m WiFi Repeater Signal Booster for $13.99 with coupon (from Banggood). Price history, coupons and price alert are available on this page. You probably want to know what is the best price?
Packing: 11.7cm * 11.7cm * 6.7cm., Name: 300M WiFi Repeater, Product: 8cm * 5.2cm * 7.5cm., Color: white / black, Technology: white glossy surface, Material: shell ABS
Latest coupon and price update (UTC):
Banggood ($13.99)
Banggood warehouse is located in China. Coupons for 300m WiFi Repeater Signal Booster? Nope, there’re no coupons in Banggood. But wait a sec… Is it a good price? This price is higher than average price ($12.49) for this item.
Link: Banggood product page
Price: $13.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGae2847, BG589b2e, BGcb5ddb
(these codes were not working in latest coupon update, but you can check them out anyway)
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
Do you need price history chart (for all/most countries) for 300m WiFi Repeater Signal Booster? There we go.
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)).