Just check coupons out (with price alert and history). Best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest price update (UTC time):
Amplifier Size: 18.6 * 9.1 * 9.8cm/ 7.3 * 3.6 * 3.9in, Power: 10W, Amplifier Weight: 780g/ 1.7lbs, Headphone Jack: 3.5mm, Model: Mighty Air, BT Distance: 10m, Charging Time: 3h, USB Power: Type-C 5V/2A, Package Weight: 1102g/ 2.4lbs, Input Impedance: 1M, Transmitter Power Supply: 3.7V/ 500mAh battery, Transmitter Latency: <5ms, Transmitter Wireless Distance: 15m, AUX In Jack: 3.5mm, Package Size: 25 * 13 * 11.5cm/ 9.8 * 5.1 * 4.5in, BT Version: 4.2, Frequency Response Range: 20Hz-22kHz, Color: Black, Transmitter Operation Frequency: 2.4G, Speaker: 10W *2 / 2 inch / 4Ω, AUX In Impedance: 22k, Input Jack: 1/4 inch Mono(also serves as a charger to charge the wireless transmitter), Brand: NUX, Playing Time: up to 18h
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($239.08): BG1d402f
2. ($249.70): BG00c906
just apply this code in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGNUX07, 7bcdf9, BGNUX0707, BANGGOODSD, BG1081b2, 00c906, BG423938, ADMITAD2212
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Check out price history chart (for all/most countries) for NUX Mighty Air Wireless Guitar Amplifier.
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)).