It's worth noting the huge Wiimote sales noted by Nintendo. In short, if Move sells okay, and the games are fun enough, Sony stands a good chance of seeing a lot of additional sales.
Heck, my kids already want me to buy 2 more wands (in addition to the two we have) so they can fight each other using 2 wands each in Sports Champions. I've resisted so far because I'm mean and I'm not even sure you can do that in SC (must check) but I'll probably crumble which means I'll have 4 wands.
If there's one thing we can draw from the Wii model, if the games are fun enough and encourage multiple controllers a lot more people than you'd think will slowly invest. While the total figure can seem huge, when you're buying a single wand at a time over a number of months it just doesn't seem like much.
I believe this is why Sony are clearly positioning Move more as a traditional peripheral controller, because in a sense it is and, should it take off well enough, this model typically drives a lot of additional (very profitable) hardware sales. With Move Sony I believe are targeting hardware sales, in addition of course to more consoles, software and PSN users.
MS are pushing Kinect more as a console launch, which in a sense it is as you would only reasonably buy one and that's it. After that the upside for MS is install base, consoles sales, software sales and hopefully more Live subscriptions. However unlike Move, at this point Kinect doesn't seem well positioned to drive addition hardware peripheral sales (and unless MS subtly change the message right now the whole 'you are the controller' make Kinect the end result, no more peripherals required - unless you really want that inflatable boat!)
With the higher entry price (even if arguably lower multiple player price) it also seems more sensible to position Kinect this way.
Anyway, like I said I think that, at least over the first three months, Kinect will see the larger install base, but Move might well see the higher individual unit sales.