Price history, coupons and price alert are available on this page. You probably want to know what is the best price?
Material: Glossy Carbon Fiber, Thickness: 0.5 / 1 / 2 / 3 / 4 / 5mm, Surface Treatment: 3K & Glossy Surface, Weave: Plain Weave, Size: 250x420mm, Tensile Strength: 3200Mpa, Color: Black
Aliexpress
I could not find it on Aliexpress. Click here to search by yourself.
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. One coupon is available. Cool!
Link: Banggood product page
1. ($44.57): BANGGOODSD
put item in your cart and apply coupon code there 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): 13f142, BGHONEY2110
(these coupons are old, so probably won’t work)
Price history and price alert
Do you need price history chart (for all/most countries) for 250x420x3mm 3K Black Carbon Fiber Plate? There we go.
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)).