I agree with Rol.
This is more to do with content on those systems than the overall form factor / price.
Price has always declined steadily and never produced that really late 2nd peak or curve for a system. However, this is the first time 3rd parties shoved all support to the "losing" console(s).
Had the Wii gained the 3rd party full support as had been the case with every generational leader previous, these charts would not be the same and Wii would have been toppling PS2 by the end of it all. Instead it dove off the cliff and the other two had late surges as Wii owners and late PS2 upgraders bought new consoles.







