Agreed. People don't get that the manufacturing of the sensors is not really any different from making CPUs or Memory. The cost is really per "wafer" used to make the sensors. As an example one standard size of manufacture is a 20cm wafer. From that wafer, if you assume no defects, you can get 24 FF sensors with about 35% of the wafer "wasted," or you can get 80 APS-C sensors with about 18% waste. So just looking at that, every FF sensor will cost AT LEAST 330% more (80/24) than every APS-C sensor, and that's not accounting for anything else. Basic economics and manufacturing would say that the difference is more than that, even - You have the same difference in R&D costs to develop the sensor assuming a number of prototyping efforts, etc.
Cost saving from the sensor is probably the only way to reduce the overall cost of the APS-C/R7 cf the R6
A new IBIS unit will need to be designed for the smaller sensor
Main benefit of a crop sensor will be pixels on target. The current M series 32mp crop sensor is much higher than the cropped R5 sensor @ ~17mp. Remember that the 7Dii is still only 20mp so not a huge difference from the cropped R5.
Whether the 32mp sensor will be reused (cheaper) or a resized version of the upcoming R5s sensor is a good question. For cost, the 32mp is fast enough already and amortised the R&D
Reusing the R6 body makes sense but they could save money for losing the joystick for instance as a differentiator. Touch/drag on the rear LCD for moving focus point may be faster and sufficient
Makes sense to use the same focusing system and shutter speed as the R5/6 for consistency/cost but the R7 can't be too good compared to the R6
No RF-S lenses. If you want to go wide then use adapted EF-S lenses. If there is to be a RF-S, expect just a cheap wide angle zoom and stellar wide angle zoom equivalent to their EF-S lens options. For long focal lengths then RF100-500mm or EF100-400mm (or EF/RF primes) together with the expected long RF primes to come.
Weather sealing equivalent to the R6
4k/30 and HD/60 with no overheating cf R6's 4k/60 and HD/120 for video differentiation. The current 32mp sensor can do 10 bit to HDMI so assume that internal 10 bit will be possible. Autofocus with HD/60
Single UHS-II card slot. Fast enough for video and continuous shooting (CFe is not needed). Differentiator to the R6's dual cards and saves money.
Would make sense to release a M7 at the same time as R7 with basically the same specs but different form factor to manage both target segments. Managing heat in the M7 will be interesting. M7 should have a built in EVF
Same battery for M and R6 variants
The unicorn of the 7D's price, focusing system from 1D, fps more than double the 5D, weather sealing from the 5D can't be supported with the current R body marketing.