People arguing that when you consider the retailers's margin the PS4 will be sold for more than $500 bucks forget that consoles margin are generally lower than 5%.
And considering Sony is not looking to block used games sales it is practically guaranteed that videogame specific retailers like Gamestop will push the PS4 and place it prominently on their stands.
$100 subsidy per unit, that means if they sold 10 million units they've be in the red for $1 Billion.
I don't think Sony can afford to lose $1 Billion up front on the console. And we're not even taking into account the marketing cost of a launch which will by itself probably cost hundreds of millions.
Sony might have been able to do it with the PS3 because they were flush with PS2 cash. But right now? I just can't see it.
You forget to mention that Sony saved a lot of money on R&D going with off the shelves parts. They were actually profitable when they marked down PS4 R&D costs. Gaming division have money and can lose money on the launch with subsides if they need to. Doesn't mean that they want to do that. Designing, developing and testing a console can cost billions of dollars.
A big chunk of the PS2 cash was spend on PS3 R&D which was way, way more expensive than R&D on PS4 if you remember they had to pay up for the development of cell and push up Bluray adoption.
Sony would gladly lose one billion in subsides if they could sell 10 million PS4s at launch. They would recoup at least 30% of it just with accessories sales, probably way more considering the good margins on those. A controller costs 20, 30 bucks at max to be made and it's sold at 50, margins on official cables are even bigger.
I'm not even mentioning game sales.