Comparisons to the current $250 16GB Nexus 7 are a bit pointless. As has already been posted, there are strong indications that the model will get a price drop before the iPad mini has reached any consumers' hands which change the value proposition.
Furthermore, the iPad mini isn't in the same class of tablet as the Nexus 7. The Nexus 7 fits in a jacket or jeans pocket which the iPad Mini doesn't; one is properly portable while the other isn't. The proper comparisons that should be made to the 4:3 7.9" iPad Mini are the 16:10 8.9" Android tablets like the Galaxy Tab 8.9. Even then the iPad Mini will have competition from the likes of the Kindle Fire HD 8.9 and the Nook HD+. The Nook HD+ will be in stores on November 1st with a 'retina-class' display and 16GB for $269. It won't feel right for me buying the first generation iPad mini for family and friends this holiday season when all they want to do is browse the web, read books, and check email, facebook and twitter when the Nook HD+ can do all that satisfactorily with a much better screen