One thing I've heard and maybe someone else can verify it is that Sony's licensing fee is $2 more than Microsoft's. Also I've heard that the cost of packaging for a PS3 game is about $1-$1.10 more per unit due to blu-ray.
So if that is true then it actually cost publishers ~$3.00 more per unit for a game on PS3 than 360. So for every million units sold on the PS3 they make 3 million dollars less than a game selling a million units on the 360.
I guess that's a little off topic but something to think about...