An APS-C sensor is much smaller area wise than a full frame sensor, you get many more sensors per wafer that way.
We are all just guessing on cost anyway, only Canon knows for sure.
Over time costs go down but not in the first offering, all the R&D are sunk into that release, along with new fabrication, prototypes, and new firmware.
Subsequent models that share that sensor come in at a lower price however.
In any case if there is a 7D RF model that comes out, it will be several hundreds more than the 7d2 launch price I am sure. Hope not, but demand is so low for digital camera gear, the price has to reflect a lower demand. It will at least be very close to the R6 price tag.
The absolutely only advantage I could see with an APS C offering in the R lineup would be a denser sensor for better cropping power. I don't see Canon making crop body lenses in the RF mount, but who knows. A 30 to 35Mpx crop body would be interesting to me as long as it has pretty close to the same ISO performance (within a stop, or under a stop), and all the same specs as the FF models, with burst rates, AF system, etc.
Then again though, it would be hard for me to spend $2500 just to get an R6 with a smaller sensor that has a higher pixel density than the R5, there would have be some sort of really good use case for me to do that. I could just go get an M6II then for much less money and use EF lenses with the speedbooster, etc. where I can convert the APS-C to a 1.1 crop when needed, or keep the 1.6 crop factor other times.





