You pay only for units that actually ship through Sub Same Day, at the per-unit price you bid, the spokesperson added. An Amazon logistics facility in UtahCharles-McClintock Wilson/NurPhoto via Getty Images Paying to Amazon has expanded the range of products available for delivery in as little as a few hours over the past year. It s not afraid to make sellers compete against each other. Vanessa Hung, CEO of Online Seller Solutions, an agency that advises Amazon sellers.