The price of a single piece of silicon that large is still ridiculously cheap, as I mentioned before. We are talking about roughly 50 US$ per 200m wafer ...
The price of the blank wafer is clearly a very small part of the sales price of the sensors made on them. That 200mm wafer would hold about 20 36x24mm sensors, for a silicon cost of about $2.50/sensor, way under 1% of the price of such sensors.
... you might need 10 of then to get one perfect one, but even that is doubtful as the processes have been perfected to incredible levels.
Do you have any basis whatsoever for that one in ten figure? We are talking about needing
1. free of fatal defects over almost the entire wafer, whereas with most chip fab., each defect only causes one of many chips to be rejected.
2. massive stitching; maybe 100 fields or so, and thus greatly increased opportunities for errors there, and complexity (repeated careful alignment after moving the stepper to each new field) in the process.
Given that puny little 44x33mm sensors cost several thousand dollars, and the yield with clearly be lower for this far larger size, we can safely scale by a factor of well over the area ratio (about 30), getting well past $100,000 I would say.
P. S. Dalsa already offers CCD sensors of about this size on a custom basis: the Canon claim is mostly big CMOS. No camera maker has ordered a 5"x4" sensor from Dalsa (or even 6x7 or 6x6 or full 645 size) again hinting that cost is a major barrier.
P. P. S. It is probably 10MP or less, going by the hint that photosite area is 100 times greater than on Canon 22MP, 36x24mm sensor.