Just check coupons out (with price alert and history). Let’s see what best price is ATM.
Tire size: 14x 2.125 inch, Motor rated power: 250W, Battery: 7.8Ah, Maximum speed: 25km/h, Mileage: 40 – 80km (40km in pure electric mode; 80km with power assist system)
Aliexpress
There’re some similar (or not) items on Aliexpress
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.
Link: Banggood product page
1. ($429.99): BGFDD1CN
2. ($590.99): 7bcdf9
coupon code has to be applied in shop’s cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): 820c20, PICODICOM, 686e69, BGFDD1CN19, bGpAnDacHeCk
(these coupons are old, so probably won’t work)
Other warehouses/versions
This item is available in 1 another warehouse/version!
1. China – FIIDO D1 Electric Bike 7.8Ah Black ($-3)
Price history and price alert
Check out price history chart (for all/most countries) for FIIDO D1 Electric Bike 7.8Ah White.
Price records source(s): Gearbest, 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)).