My social psych professor suggests a possible solution to the underpricing conundrum. She suggests that putting out a new hot system, especially around Christmas time, gets us to psychologically commit to buying one, either for ourselves or for our kids. When we discover we can't get one, we (a) decide to get one when they are available and (b) buy something else for Christmas. As a result, instead of making just one Christmas sale, the toy/video game companies make Christmas sales and, after the supply opens up, January sales.
There's at least one problem with this explanation: why would the companies assume that they'll reap the benefit of the double sale. Maybe whatever substitute we buy for Christmas will come from some other company. But, other than that, this does seem to make psychological sense.
PS: As I think about it, this doesn't help with iPhone pricing at all.