The coupon price for Radiomaster ER6 2.4GHz 6CH ExpressLRS ELRS RX 100mW PWM FPV Receiver is $30.99 (in Banggood). Go down and check coupons out. Remember to check price history if it is available. You probably want to know what is the best price?
Radiomaster ER6 2.4GHz 6CH ExpressLRS ELRS RX 100mW PWM Receiver Support Voltage Telemetry for FPV RC Drone Airplane Glider
Latest coupon and price update (UTC):
Banggood ($30.99)
Banggood warehouse is located in China. I have no active coupons for you right now. Price? This price is higher than average price ($29.11) for this item.
Link: Banggood product page
Price: $30.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BG589b2e
(probably won’t work, but you can try them out)
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 Radiomaster ER6 2.4GHz 6CH ExpressLRS ELRS RX 100mW PWM FPV Receiver? 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)).