Interesting multi-channel marketing question. We received a Tassimo coffee maker. Needing to order the T-discs to make coffee, I did a quick Google search. If you're Braun, the Tassimo manufacturer, you'd probably prefer to have people order directly from you, so that you can add them to your mailing list, and try to sell automatic shipments of coffee (very much the low priced razors, high priced razor blade model).
Negatives of the Tassimo website: it's difficult to find decaf coffee, and the free shipping on $30 ordered isn't prominently promoted.
Positives on Amazon: Prominent free shipping on $25. Bigger packages available -- 16 packs rather than 8, slightly discounted prices, and the ability to use an existing account.
If I was running the Tassimo site, I'd have a huge banner with Free Shipping on your first order, regardless of amount. The lifetime value of a customer would have to outweight whatever it costs to ship some relatively light coffee discs.