Apple isn't delivering the media. Amazon and Netflix are. They're paying for all the costs associated with it. Once you have the app (which associated costs have been paid for when the developer signed up for the SDK), the iPad is just a display.
That's incorrect in regards to Amazon, some highlights from their terms
here
How is the Kindle edition price determined?
Amazon.com determines the Kindle edition price. Publishers will receive an email notification with the pricing details prior to launch of the publication.
Effective December 1, 2010, qualifying publishers will earn an increased royalty for their newspaper and magazine titles. For each subscription sold, publishers will earn
70% of the retail price, net of delivery costs. Blog publishers will continue to receive 30% of the gross revenue.
How is my revenue share calculated?
Revenue share is calculated as (revenue - delivery costs) x 70%. Delivery costs apply if we deliver content via a paid distribution method, such as over Whispernet. When Amazon includes delivery, the cost is $0.15/megabyte (MB) in the US and UK sales from Amazon.com, £0.10/MB for sales from Amazon.co.uk and $0.99/MB in the rest of the world. We calculate the delivery cost by multiplying total megabytes sent by paid delivery by the cost per megabyte above. Delivery costs are therefore dependent upon customer location, how they chose to download and the file size.
How can I estimate my delivery costs?
Delivery costs are dependent on the Kindle file sizes. Kindle file sizes vary depending on the number of articles and images that are included in the file. The file size for a typical newspaper with 100 articles and 15 to 20 images ranges between 0.5 and 1MB. The file size will also vary depending on the resolution of the images. The file size for a typical magazine publication with 30 articles and 20 to 25 images ranges between 1 and 1.5MB. You can estimate the file size for your publication by downloading the Kindle files after you have added your publication through KPP.
For example, the delivery cost of a newspaper that delivers 9.0MB/month via paid delivery methods is $1.35. If the publication costs $9.99/month, then a publisher would earn $6.05 for each subscription.
Does this mean that publishers pay for all of the delivery costs?
No, the delivery cost is shared in proportion to the revenue split,
so publishers only pay for 70% of the delivery costs. The formula to calculate your royalties under this new revenue model is (revenue - delivery costs) x 70%.
On a personal note, I'm not sure this'll apply to Netflix, Rhapsody, etc Reading the Apple press release (as well as Google's announcement) makes me think it's more to do with digital newspapers/magazines, particularly how Apple kept mentioning publishers, which I don't think really applies to Netflix et al.
If they're really going for everyone with no exceptions, then I just hope they know what there doing.