seekingalpha.com
One thing that differentiates Amazon.com from walmart, though: Amazon.com supports individual retailers, in a serious -- and, I suppose, fun looking -- way
EDIT: I've looked at things recently that Prime didnt apply to, Torani syrups for example. These were from third party stores. It may be the individual stores option whether it participates in Prime.
2m users x $79 per year = $158 million by the way. huge. and that's just revenue from the subscription service, not including the average order increase. plus a 92% renewal rate.
re: amazon stores -- third-party amazon stores offer a great deal for retailers who want to backfill their inventory with products they don't actually carry. amazon then pays the retailer affiliate fees, and the buyer doesn't know the difference.
It definitely doesn't apply to items sold by third parties
The reason for this is that most other online merchants only ship FedEx or UPS, and their Hawaii/Alaska rates are just insane - easily exceeding the cost of whatever it is you are buying in most circumstances. Because Amazon uses USPS (as well as a service called ParcelPool), even when you want to pay for shipping in order to have a faster delivery they are still a better option.