At launch the PS4 was found to cost around $381 for sony to make. In that cost estimate processor and ram were the two single most expensive things. Both combined amounting for almost $240 of that $381 cost.
Between then and now, the amount of Ram modules on board has been cut by half (from 16 modules to 8) and the processor has shrunk to a smaller process. These two things alone can now cost as little as $100 combined for sony.
Other gains across the board; better compononet integration, smaller cooling array, removal of the optical port, smaller PCU and smaller chassis.... all yeild gains too.
So its my personal estimate that he PS4 probably cost sony around $180 right now to make. And its probably been costing them that since around august last year.
I am also convinced that this year we will see the PS4 come down in price to $199. Maybe even as early as E3. But definately this year, and the PS4pro drop to $299.
