Five BETTER reasons why 360 will have a longer life span than PS3

[Kantor]

Third parties are fickle. Once the generation changes, they stop developing for the "last generation". But first parties can always support the previous console. And Sony's first party is much stronger than that of Microsoft.

Then, of course, there's Blu-ray, which will become the dominant video format at some point, and DVD will be left behind.

Basically, the reasons you have given for the 360 lasting longer are that it's cheaper (and?) and generates more revenue. The second one is the only one with any real bearing on anything. And as time passes, components get cheaper.