Latest update shows that AC40V-300V 100A Digital Single Phase Energy Meter costs $22.69 (in Banggood). Go down and check coupons out. Remember to check price history if it is available. Best price?
AC40V~450V 100A Digital Single Phase Energy Meter Tester Electricity Usage Monitor Power Voltmeter Ammeter – AC40-300 Built-in CT
Latest coupon and price update (UTC):
Banggood ($22.69)
Banggood warehouse is located in China. I’m afraid that there’s no working coupon in Banggood. You probably want to know if this is a good price. From what I can see this price is higher than average price ($17.66).
Link: Banggood product page
Price: $22.69
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BG20236Tool
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Aliexpress
I could not find it on Aliexpress. Click here to search by yourself.
Here are coupons that you can use.
Price history and price alert
Here is price history (for all/most countries) for AC40V-300V 100A Digital Single Phase Energy Meter.
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)).