Given that Apple was spending in the order of $1 billion to store iCloud data in AWS I don't think this claim is exactly credible.
Dropbox reportedly had to move 500PB of data off of AWS which at a very naive $0.03 per GB per month would only be around $180MM per year. $0.03 is probably higher than the rate dropbox pays per GB but I'm ignoring network ingress/egress costs.
From those back of the envelope calculations I think it's safe to say that iCloud is very likely larger, or at least a similar size to Dropbox.
Dropbox reportedly had to move 500PB of data off of AWS which at a very naive $0.03 per GB per month would only be around $180MM per year. $0.03 is probably higher than the rate dropbox pays per GB but I'm ignoring network ingress/egress costs.
From those back of the envelope calculations I think it's safe to say that iCloud is very likely larger, or at least a similar size to Dropbox.
https://blogs.dropbox.com/tech/2016/03/magic-pocket-infrastr...
http://www.pcworld.com/article/3045436/data-center-cloud/app...