Basically copy coupon, view price history or create e-mail price alert. Let’s see what best price is ATM.
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):
Discharge Plug: XT60, Discharge Rate: 150C, Dimensions: 78mmx 39mmx 42mm (Lx Wx H), Configuration: 6S1P / 22.2V / 6 Cells, Minimum Capacity: 1400mAh, Charge Plug: JST-XHR, Max Burst Discharge Rate: 260C, Net Weight(±20g): 222g
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($49.72): BGToys8
2. ($49.72): BG8OFFCOUPON
3. ($49.72): TTBLACK5
you should apply the coupon in your 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): Cuponation9, BGGutscheine
(there’s a little possibility that old coupon will work)
Price history and price alert
Price history (for all/most countries) for Tattu R-Line Version 5.0 22.2V 1400mAh 150C 6S1P RC Battery XT60 is here.
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)).