New Nikon 24mp sensor (D5200) is made by.... Toshiba! New kid on the block?

As you point out it is a separate division of Sony that makes the sensors. And, with increased production, and sales, the cost of the sensor comes down. I think the reason Nikon kept coming out with new Sony sensor first, was because Nikon would order a larger quantity than Sony would, which allowed the division to write off the development costs faster, allowing Sony Imaging to buy at a lower price.

If Sony cannot sell enough sensors then it will take a longer time to recoup their R&D costs, and Sony cameras may end up costing more. And, in the end, Sony may end up buying their sensor from someone else, in order for their cameras to be competitive in the marketplace.

I'm sure you've heard of Samsung being sued by Apple for patent infringement. Apple won a suit against Samsung where they claimed that Samsung was copying the design of their iPhone. Samsung was ordered to pay billions.

However, another division of Samsung continues to sell many of the components that Apple needs for the iPhone and iPad.

Many people on this forum thinks that Sony Imaging gets their sensors for free. But, Sony Imaging has to pay the going price for the Sensors that the sensor division charges. They don't get a discount that Nikon or anyone else wouldn't get.