Not a fair comparison, given that 5S + 5C is two models.
It would be fairer to compare it to the sales of the 5 + 4S last year - which were probably not 9 million, but certainly more than 5 million.
So to get the real comparison you need to add first weekend sales of the 4S in standard launch countries and China to that 7 million figure.
http://www.apple.com/pr/library/2012/09/24iPhone-5-First-Wee...
I'm not implying that Apple didn't do a great job by moving to the 5S/5C split, just that it'd be fairer and more useful to compare 5S/5C to 5/4S and 4S/4 - if only for the fact that it doesn't leave any room for pedants like me to argue :-)
I realise 5S supply would be very, very constrained initially... so how well did introducing the 5C unconstrained at launch work?
I think the 'champagne' phone would have sold out in the launch weekend, regardless of supply. Is Apple playing this out? (yes).
Every customer lining up, or entering stores are dropping almost a grand. You want to keep some top tier 64gb 'space grey' in stock, to sop up those who missed out on a different alloy.
And everyone who isn't eligible to upgrade? Well you get a fantastic OS, and you can buy a nice case! Well played Apple. And I mean that without bitterness. Great product launch.
This article is claiming that most of the phones sold are 5S's, actually... which would mean the 5C is making a moderate difference to that number... just enough to bump from 7 million to 9 million, perhaps!