This AUKEY 20,000mAh Portable Charger drops from $37.99 to $29.99 and then to $22.99 when you use the code 2AUPOWER during checkout at Amazon. Shipping will add $5.99 or is free with an Amazon Prime account. However, even with shipping added, this is still the lowest price we could find for a power bank of this capacity that also has a built-in Lightning input and dual 2.4A USB outputs. These power banks have built-in safeguards that protect against excessive current, overheating, and overcharging, and a large enough battery to fully recharge two iPads simultaneously and do it at normal charging speeds. Sales tax is charged in most states.