You can create price alert here, copy coupons and view price history. Let’s see what best price is ATM.
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):
2 in 1 Dust Box Water Tank: 260ml(Water Tank)+300ml(Dust Box), Suction Adjustment: 3gear, Voice Control: Only Supports Chinese, Power: 42W, Water Volume Adjustment: 3gear, Battery Capacity: 5200mAh, Brand: Xiaomi Mijia, Wireless Connections: Wi-Fi IEEE 802.11b/g/n 2.4GHz, Suction: 4000Pa, Host Model: MJSTS1, Dust Box Capacity: 550ml, Application Area: 250m², APP Control: Yes, CMIIT ID: 2021DP0745, Battery Type: Li-ion battery, Voltage: 100-240V 50/60Hz 0.8A, Charging Base Model: CDZS1
Banggood
Banggood warehouse is located in China. We have found one coupon for this product!
Link: Banggood product page
1. ($599.99): BGCNXMPU
this code has to be applied in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGCNXMPRM, 7bcdf9, BG10OFFAFF, BGCNXMSPR, BGCNNEWXM, BGwhielabel, BGCNXMP, BGCNXMUPA, BGCZXMSTP, BG10OFFAFF1, BGHU0775, BGCZXMPRE, BGCNXMSR, BGCZTAXMP, BGCZXMPR5, BGCZXMPT, BGDUXMCPR, BGCZBFXMP, BGBFCZMP, BGCZPLMP, BGCZPLXMPE, BGCZPLXMPV, BG49c64a, BGIT202203, BGGR2202, BGIT2222, BGHU1708, BGc03d95, BG64a506, BG4a9f05, Terence, BGDC0304, BG1dfbbc, BGcabddf, MVC8SPRING, BGf6521b, BGb8a9e8, BGmiproB, BGmiproA, BG622yb29, BGPLXMPU, BGjune30d, BGmiproDYF08, BGjuly12e, BGxiaomipro
(I don’t think these’re gonna work, but you can try ’em out anyway)
Other warehouses/versions
This item is available in 1 another warehouse/version!
1. Europe – Xiaomi Mijia MJSTS1 Pro Robot Vacuum Cleaner [EU] ($-3)
Price history and price alert
Here is price history (for all/most countries) for Xiaomi Mijia MJSTS1 Pro Robot Vacuum 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)).