Inverness has had a large influx of central-belt/English origin (my family). A lot of these people already support a team (my dad supports Morton and I know a family of Dundee fans). But like me, the younger new generation of Invernessians are growing up with ICT as their home club. And like I said in another thread, this will eventually lead to a new, vibrant support.
I'm not surprised by Ross Countys attendance figures. Like CaleyD said, a lot of it is to do with novelty factor. Also they are called ross county because they gain their support from all over Ross-shire. If you added the populations of Dingwall, Fortrose, Alness, Tain, Maryborough, Beauly etc it would easily come to c.60,000. Not to mention a large number of deluded invernessians, or more specifically 'ex-jaggies' support county