This post has two contradictory quotes in my opinion:
"It’s worth noting that this AWS price wouldn’t be what Facebook paid in this hypothetical situation. Much like Snapchat and Netflix, Facebook would be a heavy and influential user"
"Facebook’s years of specialization for running Facebook are in contrast to AWS, whose storage is designed for multi-purpose (albeit-heavy) use." - Amazon already has several tiers of storage (S3, S3 - Infrequent Access, Glacier, CloudFront)... who is to say that they wouldn't be motivated to introduce more classes by a large customer like FB.