Just check coupons out (with price alert and history). What is the 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 coupon code price check (UTC time):
Working Voltage: 110/220V, Capacity: 10L, Dimensions: 380*290*280mm, Ultrasonic Frequency: 40KHZ, Heating Power: 200W, Outer Packing Size: 435*360*350mm, Inner Tank Size: 300*240*150mm, Material: Stainless Steel, Net Weight/Gross Weight: 7.3/8.4kg, Ultrasonic Power: 240W
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($283.77): BGGutscheine
2. ($286.89): BG8ReviTrage
3. ($286.89): BGcoupon8off
paste coupon code in your cart and click Apply 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): BgcLuBofErtA10, BGAFF10OFF, BGCuponation10, 7bcdf9, BGHONEY2110, BGOxy10, BG564c1f, BANGGOODSD, ADMITAD2212, 2022ACTIESNL, Terence, Tabby20, 2203ActiesNL, BG1efeb0, 8Couponsde, MVC8SPRING, 8BGwbg2204, BG2462de, tRaDetRaCKeR, 8wEbgaInS5, pROMo8cuPoN, hoNEYbGdeAlS, BgGoodie9
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
Price history and price alert
Here is price history (for all/most countries) for SKYMEN 040S 10L Ultrasonic Cleaner.
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)).