Had small talk with my source in the industry about cost to produce and pricing of full frame cameras.

If you remove Sony sensor price difference, actual cost to production for camera increase only $5-10 as you move from m43 or APS-C. But this is the case of same number of bodies being made. Cost to produce also increases due to much smaller amount of bodies sold and hence equipment and tooling takes larger portion in each body cost. Yet for popular models this effect is tiny.

Most of extra cost presently go to Sony as part of sensor price (and most of them for FF sensors go to profits), and all else go to marketing and manufacturer profits. Some recent bodies reached record ever profit margins, such that some top management had been able to buy very big condos only on one year end reward money.

Another part is camera LSI, main chip doing all the work. All camera companies are now reluctant to make new chips at proper pace and using latest processes (10-14nm in camera LSI case). Sony plans to get ahead playing on such management errors. By introducing patented proprietary sensor interface they will also now demand buying their own LSI.

Rumors are that Panasonic S1 and S1R can be first camera not having anything from Panasonic except interface and small amount of firmware changes. Cameras will run on fully Sony sensors and Sony LSI, as well as will have Sony color science for first time. In return Panasonic will get special terms for LSI and sensors, discount can reach 40%. But thus leak are well below 100% certain, that is certain - lower end models will have Sony LSI and color science.