Price history, coupons and price alert are available on this page. What is best price?
Call: about 6 hours, Sounding unit: 6mm customed hifi miniature full screen unit, White, Acoustic diaphragm: graphene carbon nanotube diaphragm, Frequency response range: 20Hz-20KHz, Material: TPU, Standby: about 40 hours, Colour: Black, true wireless stereo, Magnet type: Rubidium iron boron, Acoustic structure: closed, waterproof and dustproof, General: HIFI sound quality, adaptive noise reduction
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):
Banggood
Banggood warehouse is located in China. Well, there is one coupon available right now.
Link: Banggood product page
1. ($36.58): BGBuscape01
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
Old coupons (from the oldest to the newest): BGHM50, AFfbG10, affbg10, 502C6B, BGCITYADS2019, BGBK15, BGBAK15, BGdragonBoat, BG11SHOP, BG4BW25, BGLOAC1, 13f142, BGa0b145
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Price history (for all/most countries) for HM50 Wrist TWS Graphene Earphones 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)).