According to my DB the lowest price is 18.99 USD for 50X-1000X Wired Digital Microscope (in Banggood). Just check coupons out (with price alert and history). Best price?
Latest coupon and price update (UTC):
Banggood (18.99 USD)
Banggood warehouse is located in China. I don’t think there is an active coupon right now – at least in my database. Low/high price?
Link: Banggood product page
Price: 18.99 USD
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BG7fbb88, BGf40ef2, BGd192e0, BGGines, BG63d82e
(these codes were not working in latest coupon update, but you can check them out anyway)
Aliexpress
Click here… to search for 50X-1000X Wired Digital Microscope on Aliexpress
Here are coupons that you can use.
Price history and price alert
Here is price history (for all/most countries) for 50X-1000X Wired Digital Microscope.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).