$41.99 – that is current price with coupon for 420W DC 12V 35A Inverter (in Banggood). Just check coupons out (with price alert and history). Let’s see what best price is ATM.
Latest coupon and price update (UTC):
Overload Protection: Yes (120A), Input Voltage: 12 VDC, Input Current: 35A, Output Frequency: 20-120HZ adjustable, Effective range: 1-2 meters, Color: Yellow, Output Waveform: sine wave, Security protection: 12 intelligent security protections, Pulse Width: 1%-12% adjustable, Size: 200 * 100 * 50mm, Gear: frequency conversion / high voltage / low voltage, Drive: Intelligent drive computer board, Power: 68000W, Battery: 12 V DC (any model) (not included)
Banggood ($41.99)
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. Isn’t it too expensive? This price is higher than average price ($16.99) for this item.
Link: Banggood product page
Price: $41.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BG8OFFCOUPON, TTBLACK5, BG589b2e, BGET12, BGET10, BG8FORMULAMX
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
Aliexpress
There’re some similar (or not) items on Aliexpress
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 420W DC 12V 35A Inverter 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)).