The Host Weight: 130g, Charging time: 900mAH, Color: White, Adapter: Input AC 100-240v 50/60hz, Size: 175.4*43*53mm(host), Working frequency: 1Mhz, Key: 2 IN 1 Power/Gear Switch, Brand: COSBEAUTY XIAOMI Ecological Chain Brand, 7.4V (3-4 hours), Usage time: 12min, output 12V 1A, Power: 5W.
Basically copy coupon, view price history or create e-mail price alert. Let’s see what best price is ATM.
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
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.
Link: Banggood product page
1. ($461.69): BG10OFFAFF
2. ($503.99): 7bcdf9
apply it in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): 502C6B, vipupgrade8, ML15%Pro, BGHC20, bgshOOp10, bGhOnEy10, BGHB20, BgoFErTaSchInA10, BGSD52469, BgcLuBofErtA10, BGAFF10OFF, BGCuponation10
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Here is price history (for all/most countries) for Xiaomi CosBeauty PerfectGlow Skin Revitalizing Device. The lowest price was: $349.99.
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)).