You can create price alert here, copy coupons and view price history. Do you want to know what the best price is?
100us-2900us@33-1000Hz @S1-S4, 5.8-8.4V@MAX 4A(S1-S4), Output Signal: , Main Output Voltage: 5.0-28.0V@MAX 10A, P1 Button: 1000-2000us @P1, Product Size: 96*68*26mm Approx., Net Weight(Approx): 140g, PPM 8CH @S5, Load(max): 100W, Display: 2.4″ TFT RGB LCD Screen(320*240 resolution), Micro USB: Update@USB3.0, Packing Size: 105*80*45mm Approx., Gross Weight(Approx): 160g, 5.0-8.4V@MAX 2A(S1-S4), SBUS 16CH @S5, Channel: 8CH Output, Signal Output Voltage: , Input Voltage: 7.0-28.0V@MAX 10A, PWM 500us-2500us @S5
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($54.04): BGToys1
2. ($55.25): BGRCParts8
coupon code has to be applied in shop’s 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): BGST810, Parts8, AFfbG10, BGST812, BGST81, BGTOOL812, BGST815, BGTRC812, BGAFF10OFF, bGhOnEy10, BGCROOT1, bgshOOp10, BgcLuBofErtA10, BGCuponation10, BGHONEY2110, BGDAVIS, Tabby20, BG1efeb0, 8BGwbg2204, tRaDetRaCKeR, pROMo8cuPoN
(probably won’t work, but you can try them out)
Price history and price alert
Price history (for all/most countries) for ToolkitRC ST8 RC Servo Tester is here.
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)).