Cost per unit of Amazon US products: cheapest per oz, count or GB, and each category's median.
Free
One server, in e-commerce. Cost per unit of Amazon US products: cheapest per oz, count or GB, and each category's median.
E-commerce
Cost per unit of Amazon US products: cheapest per oz, count or GB, and each category's median.
The rest either hold an API key issued by the publisher or ask for nothing.
Listed without a verification tick. Read the listing before installing.