I don't think this is true long term. The cheapness of cloud applies when and where deploying otherwise complicated systems - eg. a hadoop cluster - can be done in matter of clicks, but for something simple - file storage - I'm finding it hard to believe that it's cheaper. However, in case of apple, geo distribution and locality is probably very important, which adds to the cost for sure; I'd still be surprised if long term own/rented hardware wouldn't be cheaper, than SaaS.
Especially for object storage. The scale where deploying your own object storage network gets cheaper than S3 is surprisingly small. Even handling your own equivalent of "intra-zonal redundancy" is easy. The main concerns arise in "how do you CDN that data to your customers" and "how do you gain redundancy beyond intra-zonal"; that's where S3/GCS gets more interesting.
Who is saying they aren't going this avenue? It would make sense to me that they would slowly increase their own infrastructure, testing it's reliability and over time decrease their reliance on third parties.
Apple has enough money to tread carefully and roll things out slowly.
