5) Nothing to Join, Free Service of Amazon Prime. Prime Pantry is a service that is included in the $99 fee that folks pay for Amazon Prime. IMPORTANT NOTE: Even though Pantry Prime is part of Amazon Prime which offers free 2-day shipping, you have to pay for shipping. It's a flat rate of $5.99 for a box that is 4 feet wide by 4 feet high. Which is a generous size, big enough to hold four 10-pound bags of cat litter.