Just check coupons out (with price alert and history). Let’s see what best price is ATM.
Weight: 833g (without battery), Item: RC Transmitter, Operating Temperature: -10℃~60℃ (14℉~140℉), Internal RF module: TANDEM, Resolution & Frame Rate of HD VTX: 720P 60FPS, USB Adaptor Voltage: 5V+0.2V, Backlit touchable LCD resolution: 800*480, Operating system: ETHOS, Brand: FrSky, USB Adaptor Current: >2.0A, Dimension: 213*200*95 mm (L*W*H), , Operating Voltage Range: 6.5 ~ 8.4V (2S Li-battery), Compatibility: ACCST D16 & ACCESS & TD series receivers, Model: Tandem X20HD, Number of Channels: 24 channels
Aliexpress
There’re some similar (or not) items on Aliexpress
| Image | Product (link) | Price | Coupons |
|---|---|---|---|
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FrSky Tandem X20HD Updated FCC/EU Radio Controller Digital Telemetry Transmitter for RC Aircraft Model | $792.33 | – |
Click here to search by yourself. Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. Only one coupon available!
Link: Banggood product page
1. ($699.65): BGRADIORU
you should apply the coupon 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
Price history and price alert
Here is price history (for all/most countries) for FrSky Tandem X20HD RC Transmitter ETHOS.
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)).