This is a frequently asked question on Prince forums. I was after a cloud guitar too, so I lurked on those boards accordingly. From what I understand, his website is subscription only and once you're in you can order a cloud.
There is another company (I forget who) who sells cheaper versions, but by all accounts they're lacking in quality.
Stupidly expensive from what I recall. I kinda gave up the search when I realised I wasn't even going to get a particularly sophisticated axe; I'm aiming for another Jem or probably a Parker.
What concerned me was that for every person who said the official guitar is an excellent one, there was another person saying it was overpriced nonsense.
Now, this could mean that the people who stumped up for the official cloud were fooled by the marketing or maybe it meant that the people who went for the unofficial cloud were jealous.
I couldn't find anyone on the boards who seemed to know much about guitars! It wasn't like Jemsite (i.e. full of players); it was populated by "collectors" (shudder).
Basically it's a bit of an almighty mess. Read the Cloud FAQ here, and change your name occasionally to some weird symbol. Everything'll be fine.