Aliexpress
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
Coupon (76.39 USD): BGTOYSALES
Coupon (79.79 USD): BG00c906
(CouponsFromChina.com tip: 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
Old coupons (from the oldest to the newest): AFfbG10, BGVDay10%off, BGAFF10OFF, BGEC13, BGTT10, bGhOnEy10, BGdragonBoat, BGSS10%SW, bgshOOp10, BGRC902, BgoFErTaSchInA10, BgcLuBofErtA10, BGSHIYI33, BGCuponation10, 13f142, BGHONEY2110, BANGGOODSD, BGc7b765, 00c906, ADMITAD2212, 2022ACTIESNL, Terence, Tabby20, 2203ActiesNL, BG1efeb0, 8Couponsde, MVC8SPRING, 8BGwbg2204, tRaDetRaCKeR, 8wEbgaInS5, pROMo8cuPoN, BG8RCToy
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Price history (for all/most countries) for Xiaomi DIY Hydraulic Excavator is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).