I'm not sure I agree with those Guardian numbers.
The PS2 is still making a lot of money true but lets not forget that the average price of any PS2 games has dropped a lot( it's rare to see new PS2 titles at 50$ these days) so the licence fee that Sony gets per PS2 title sold must have dropped too...
As for the PSP it's selling a lot but is Sony really making that huge of a profit per PSP sale ? Not so certain...