List price is $49.99 and RAVPower is respected in terms of batteries and power banks.
There is an option on the page to apply "Applicable Promotions", just click to enable
The promotion says:
Just Pay $39.99 for RAVPower 10000mAh Car Jump Starter 400A Peak Current offered by Sunvalleytek Brand
There's also a promotion to add a USB car charger for free, but I couldn't get that promo to work, it still charged me for it, so I just removed it from cart.