$45.99 – Material: ABS + PCB, Theoretical standby: More than 2.5 years, Battery working cycle life: 1000 cycles, Battery capacity: 5000mAh, Size: About 112x80x30mm/4.41×3.15×1.18in, Full charging time: 2 hours, Overcurrent protection: 1.12KA, Voltage: 4.2±0.05V, Welding current: 6-800A, Standby current: 20uA, Battery life: 800-2000 times.
According to my DB the lowest price is $45.99 for Spot Welder Machine 0.1-0.15mm Nickel Welding Machine (in Banggood). Basically copy coupon, view price history or create e-mail price alert. Best price?
Latest coupon and price update (UTC):
Banggood ($45.99)
Banggood warehouse is located in China. There are no active coupons for this product, but the price is pretty low isn’t it? I think you want to know if the price is good. My database says that it’s pretty good price, coz average is $48.10.
Link: Banggood product page
Price: $45.99
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BGd2f208, BGET12, BGET10, BGCAPITALOS8, BGCOUPERT8, BG8FORMULAMX, BG124578, BGPowerTLS2
(these codes were not working in latest coupon update, but you can check them 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
Here is price history (for all/most countries) for Spot Welder Machine 0.1-0.15mm Nickel Welding Machine. The lowest price was: $44.99.
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)).