According to my DB the lowest price is 13.01 USD for 40×60 Monocular Telescope (in Banggood). Basically copy coupon, view price history or create e-mail price alert. Best price?
Latest coupon and price update (UTC):
Banggood (13.01 USD)
Banggood warehouse is located in China. I can’t find any active coupons for this product in Banggood. Is it cheap? Hmmm, price is higher than average (which is 12.46 USD right now), so better set price alert down below…
Link: Banggood product page
Price: 13.01 USD
Old coupons (from the oldest to the newest): BG79d8fb, BGe9918e, BG4dd793, BGd1933f, BG00c906, BGFEU58, BGbfa5d1, BG09a2fb, BG475142, BGef7187, BG6FEB2023C, BBGef7187, BG5568b7, BG4c3ab9, BGc28268, BG589b2e
(there’s a little possibility that old coupon will work)
Aliexpress
Click here… to search for 40×60 Monocular Telescope on Aliexpress
Here are coupons that you can use.
Price history and price alert
Price history (for all/most countries) for 40×60 Monocular Telescope is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).