Well, in the NSA's eyes, that main difference is important. Free (and highly pushed by the very popular iPhone and iPad) meant people actually starting using iCloud. The cost-benefit analysis shifted tremendously from .mac/MobileMe.
It is fun to think of Steve Jobs as the lone person saying "fuck you" to the NSA. But it isn't realistic. It isn't like the other companies are run by meek people who love bending over to authorities.
I can remember that I've had a free .me account before iCloud, so I believe even .me must have had enough users: it was freely available to every iDevice user. There were millions of them fast.
How does that follow? It is not just about the cost, but the amount of utility for the NSA. There are plenty of free services that are not on the PRISM list and I am sure even Apple employees would freely admit their pre-iCloud user numbers were disappointing. They would not have bothered to rebrand the service in the first place if they had a significant userbase.
Looking at the PRISM company list, we are talking data service companies with users in the tens of millions (minus the oddball Paltalk). Apple just wasn't in that group until recently.
It is fun to think of Steve Jobs as the lone person saying "fuck you" to the NSA. But it isn't realistic. It isn't like the other companies are run by meek people who love bending over to authorities.