Max. Magnification: Approx. 0.21 times, Lens Construction: 5 Groups 6 Elements, Min. Focusing Distance: Approx. 0.35m, Package Size: 10.5x 10.5x 9.8cm / 4.1x 4.1x 3.8inch, Angle of View: 46° (Diagonal) / 27°(Vertical) / 40°(Horizontal), Item Weight: 190g / 6.7oz (with covers), Max. Diameter and Length: Approx. φ75x 51mm, Filter Diameter: 58mm, Diaphragm Blade: 7pcs, Brand: YONGNUO, Package Weight: 290g / 10.2oz, Model: YN50mm F1.8 II, Minimum Aperture: f/22, Focal Length: 50mm, Driving System: Direct Current Motor: .
Basically copy coupon, view price history or create e-mail price alert. Best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. So I have checked for active coupons (all category coupons and old ones), but there was no working coupon in Banggood.
Link: Banggood product page
Price: $-3
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BGd0b05d, BG2589f4
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Here is price history (for all/most countries) for YONGNUO YN-50mm F1.8 II AF MF Canon Lens. The lowest price was: $79.99.
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)).