$264.50 – ISDT K4 AC 400W DC 600W Dual Mode Smart Balance Charger for 1-8S LiPo Battery – EU Plug.
I have just checked coupons. The lowest price I could get is $264.5 for ISDT K4 AC 400W DC 600W RC Balance Charger (in Banggood). Go down and check coupons out. Remember to check price history if it is available. Let’s see what best price is ATM.
Latest coupon code price check (UTC time):
Banggood ($264.50)
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. Price? Well, this price is higher than average price ($191.16)
Link: Banggood product page
Price: $264.5
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BGSPRING8OFF, BGHONEYSP, BGESJY8, BGALL8
(I don’t think these’re gonna work, but you can try ’em out anyway)
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.
Price history and price alert
Price history (for all/most countries) for ISDT K4 AC 400W DC 600W RC Balance Charger is here. The lowest price was: $167.99.
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)).