Basically copy coupon, view price history or create e-mail price alert. 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):
Brand Item: FlySky, Wireless frequency: 2.4GHz ISM, Item Name: FS-ST8 Radio Transmitter with FS-SR8 Receiver, Model: fixed-wing / deltas-wing / glider / helicopter / multi-axis / FPV / car model / engineering vehicle / robot / boat, Model: FS-ST8, Wireless protocol: ANT, Channels: 8-10, Transmission power: <20 dBm, Version: Standard Version/Upgraded Version
Banggood
Banggood warehouse is located in China. Only one coupon available!
Link: Banggood product page
1. ($84.63): BGAUGUST8
apply code in your basket (cart) after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
There were country-specific coupon codes published on Couponsfromchina social channels and price alerts. Coupon price may vary by country, because there’re different VAT rates, shipping cost etc. There is a chance that some latest coupons are still working:
Old coupons (from the oldest to the newest): BGRADIORU, BGToys8, BGSaleFeb8, BGSaleAD, BGMatt2022, BGMARCHSALE, BGToySale, BG589b2e
(these coupons are old, so probably won’t work)
Other warehouses/versions
This item is available in 1 another warehouse/version!
1. Europe – FlySky FS-ST8 2.4GHz 8CH ANT RC Transmitter with FS-SR8 Standard [EU] ($-3)
Price history and price alert
Here is price history (for all/most countries) for FlySky FS-ST8 2.4GHz 8CH ANT RC Transmitter with FS-SR8.
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)).